Sourdough Discard Butter Swim Cornbread (The Best Summer Side)

If you have never made a butter swim before, here is the whole idea: you melt the butter right in the pan, pour the batter straight on top of it, and do not stir. The butter climbs up the sides while it bakes, fries the edges crisp, and then soaks back into the crumb as it cools.

This has become the side dish I make when we grill out. It goes on the table next to steak and it disappears before the steak does. My husband takes a corner piece every time and my kiddos fight over the sugared top.

And it uses up half a cup of sourdough discard, which is the part I love. That tang is what keeps this from being another sweet cornbread that tastes like cake. It sits underneath the butter and the sugar crust and gives you something to come back for.

Why we brown the butter first

Most butter swim recipes have you melt the butter in the oven while it preheats. That works fine in a metal baking dish. In cast iron it is a different story, because the skillet takes a long time to come up to temperature and the butter sits there the whole time inching toward scorched.

So we do it on the stovetop instead, and we take it one step further. Melt the butter over medium low and let it go until the milk solids just turn blonde and it smells nutty. That takes 3 or 4 minutes and it is the single biggest flavor upgrade in this recipe. Browned butter against sourdough tang is a genuinely lovely pairing.

Reach for a butter with higher butterfat if you have one. When butter is this much of the recipe, you notice it. Less water means less spitting in the pan and more of those toasty milk solids at the bottom, which is where all the flavor lives.

Watch it. Browned butter goes from perfect to burnt in about thirty seconds, and there is no saving it once it does.

About that sourdough discard

Use unfed discard straight from the fridge. You do not need active starter here. All of the lift comes from the baking powder and baking soda, so a sleepy discard that has been sitting in the back of the fridge is perfect.

On the sugar

I want to say something about this because it is where I landed after a few tries.

There is very little sugar in the crumb here compared to most sweet cornbread recipes. Just ¼ cup of brown sugar. That is on purpose. The sugar on top is doing the sweetening. It hits your tongue first and undissolved, so it reads far sweeter than the number suggests, and it means the crumb gets to stay tangy and corn forward instead of turning into cake.

That contrast between the crackly sweet top and the tangy crumb underneath is the entire recipe. If you sweeten both, you lose it.

Use unrefined cane sugar for the top. The crystals are bigger and they keep their molasses coating, so they survive the bake and give you actual crunch. Fine white sugar dissolves into the buttery surface and you get a tacky sheen instead of a crust.

Ingredients and equipment

This is written for an 8 inch cast iron skillet.

Here is everything you need so you can shop your pantry before you start. I have listed both cups and grams for anyone who likes to weigh.

This post contains affiliate links, in which I may earn a small commission at no additional cost to you. Thanks for your support!

Dry ingredients:

• ¾ cup (90g) all purpose flour
• ½ cup (70g) medium grind cornmeal
• ¼ cup (50g) brown sugar, packed
• 1 tsp (4g) baking powder
• ½ tsp (3g) baking soda
• ¾ tsp (5g) salt

Wet ingredients:

• ½ cup (120g) sourdough discard, unfed
• 6 Tbsp (90g) buttermilk
• ⅓ cup (80g) sour cream
• 1 large egg plus 1 large egg yolk, room temperature
• ¾ tsp (3g) vanilla extract

For the pan and the top:

• 6 Tbsp (85g) butter
• 2 Tbsp (25g) unrefined cane sugar, for topping
• Flaky salt, for finishing (optional but so good)

Equipment:

• 8 inch cast iron skillet
• Two mixing bowls (one for dry, one for wet)
• Whisk
• Silicone spatula
• Instant read thermometer
• Wire cooling rack

Making the cornbread

Step 1: Preheat the oven

Preheat to 350F. Slide a sheet pan onto the rack below where the skillet will go. A butter swim in a sloped skillet can bubble at the edges, and this saves you scrubbing your oven floor. This also prevents the bottom of your cornbread from browning too much, try not to skip this step.

Step 2: Combine the dry ingredients

In a bowl, whisk together the flour, cornmeal, brown sugar, baking powder, baking soda, and salt. Break up any lumps of brown sugar with your fingers and make sure the leaveners are evenly distributed. This is a small step that pays off in an even rise.

Step 3: Combine the wet ingredients

In a separate bowl, whisk the egg and the extra yolk until broken up, then add the sourdough discard, buttermilk, sour cream, and vanilla. Whisk until smooth with no streaks of sour cream left.

Step 4: Brown the butter in the skillet

Put the butter in your 8 inch cast iron skillet and set it over medium low heat. Let it melt, then keep going until it foams, the foam subsides, and the milk solids at the bottom turn a light golden brown. It will smell nutty and slightly caramel.

Take it off the heat and set it aside while you mix. Do not preheat the skillet in the oven and do not pour the butter out. It stays right where it is.

Step 5: Bring the batter together

Pour the wet into the dry and fold with a silicone spatula just until no dry flour is visible. The batter should be thick but still pourable. If it will not pour off the spatula, add buttermilk one tablespoon at a time until it does.

Lumps are fine. Stop as soon as the flour disappears, because overmixing develops gluten and the cornbread turns tough instead of tender.

Work quickly from here. The baking soda starts reacting the moment it meets the discard and buttermilk, so this batter does not want to sit on the counter while you take pictures. Get it into the skillet and into the oven.

Step 6: Pour the batter onto the butter

Pour the batter directly on top of the browned butter and spread it into an even layer. Do not stir it in. Butter will rise up around the sides and pool at the edges and it will look wrong. It is not wrong. That is the whole method, and that butter is what gives you the crispy fried rim.

Step 7: Sugar the top

Sprinkle the unrefined cane sugar evenly over the batter. Do not skip this and do not skimp on it. That sugar is the crackly, sparkly crust, and with as little sugar as there is in the crumb, it is doing real work.

Step 8: Bake

Bake for about 30 to 36 minutes.

Like with all of my recipes, go by the color, not the clock. Cast iron holds heat differently than a baking dish and every oven runs a little off, so I lean on my thermometer here. You want 200 to 205F in the center. The top should be deep golden, the edges crisp and pulling away from the skillet, and the butter no longer pooling. If the top is browning fast but the center is still wet, tent it loosely with foil and keep going.

Step 9: Rest before you cut it

Let it sit in the skillet for at least 15 minutes. I know. But any butter still sitting at the edges gets pulled back into the crumb during that window, and if you cut too early you get greasy wedges and a dry middle. It is worth the wait.

Serve it warm, straight out of the skillet, with flaky salt scattered over the sugared top.

A few more tips

On the cornmeal. Medium grind is my preference for texture you can actually feel. Fine grind gives you a softer, more cakelike crumb. Coarse grind is gritty in a way my kids complain about, so I skip it.

On the buttermilk. No buttermilk in the fridge? Whole milk yogurt thinned with a splash of water gets you close. Regular milk with a spoonful of vinegar works in a pinch, but you lose some of the tang and the tang is the point here.

Make it your own. A handful of sharp cheddar and a chopped jalapeño folded in at the end turns this into something else entirely, though I would drop the sugar topping if you go that direction.

Want it sweeter? Bump the brown sugar to ⅓ cup and drizzle honey over the warm wedges at the table. I like keeping the honey out of the batter, because it holds moisture in the crumb and that is the last thing this recipe needs.

Storing leftovers. Cover and keep at room temperature for up to 2 days, or in the fridge for up to 4. Reheat individual pieces in a 300F oven for about 10 minutes to bring the edges back. The microwave works but you lose the crisp.

Made this recipe? I would love to know how it turned out! Your rating helps other mamas find the best recipes.