Sourdough Mac & Cheese Casserole

If there’s one dish that defines cozy, comforting food, it’s baked mac and cheese. And if you’re a sourdough lover looking for a unique way to incorporate your starter or discard into more than just bread, this baked sourdough mac & cheese casserole is about to blow your mind.

This recipe transforms the classic creamy, cheesy pasta casserole into something even more flavorful by incorporating sourdough goodness. Whether you’re using active starter or discard, you’ll end up with a casserole that’s rich, tangy, gooey, and perfect for potlucks, holiday meals, or weekday dinners.

Let’s dive into everything you need to know to make the ultimate baked sourdough mac and cheese casserole.

Why You’ll Love This Sourdough Mac & Cheese Casserole

• Comforting and nostalgic – Classic mac and cheese with elevated flavor.

• Sourdough adds depth – The starter brings a subtle tang and added texture.

• Great use for discard – Perfect way to repurpose your sourdough leftovers.

• Make-ahead friendly – Assemble in advance and bake when ready.

• Customizable – Add bacon, veggies, or different cheeses to switch it up.

Ingredients You’ll Need

For the Pasta:

• 1 lb elbow macaroni (or pasta of choice)

• Salted water for boiling

For the Sourdough Cheese Sauce:

• 1/2 cup unsalted butter

• 1/2 cup all-purpose flour

• 1 cup sourdough starter discard (100% hydration)

• 4 cups whole milk (warmed)

• 1 tsp Dijon mustard

• 1/2 tsp garlic powder

• 1/2 tsp onion powder

• Salt and pepper to taste

• 4 cups shredded sharp cheddar cheese

• 1 cup shredded mozzarella cheese

• 1/2 cup grated Parmesan cheese

For the Topping:

• 1 1/2 cups sourdough breadcrumbs (see instructions below)

• 2 tbsp butter, melted

• 1/2 tsp paprika (optional)

How to Make Homemade Sourdough Breadcrumbs

Making sourdough breadcrumbs is super easy and adds even more sourdough flavor to your casserole topping.

1. Preheat oven to 300°F (150°C).

2. Tear or cube stale sourdough bread into pieces.

3. Spread on a baking sheet and toast in the oven for 15–20 minutes, or until dry.

4. Let cool, then pulse in a food processor until coarse crumbs form.

Store extra crumbs in an airtight container for up to two weeks.

Step-by-Step Instructions

Step 1: Cook the Pasta

Bring a large pot of salted water to a boil. Cook pasta until just al dente (it will continue to cook in the oven). Drain and set aside.

Step 2: Make the Sourdough Cheese Sauce

1. In a large saucepan over medium heat, melt the butter.

2. Whisk in the flour and cook for 1–2 minutes to form a roux.

3. Add the sourdough starter and cook another 1–2 minutes, whisking continuously.

4. Gradually pour in the warm milk, whisking to avoid lumps.

5. Stir in the mustard, garlic powder, onion powder, salt, and pepper.

6. Simmer for 5–8 minutes, until thickened.

7. Remove from heat and stir in the cheeses, mixing until melted and smooth.

Step 3: Combine Pasta and Sauce

In a large mixing bowl or pot, combine the cooked pasta and sourdough cheese sauce. Mix until every noodle is coated in cheesy goodness.

Step 4: Assemble the Casserole

1. Preheat your oven to 375°F (190°C).

2. Grease a 9x13-inch baking dish.

3. Pour the mac and cheese mixture into the dish.

4. In a small bowl, combine the breadcrumbs, melted butter, and paprika.

5. Sprinkle evenly over the top of the casserole.

Step 5: Bake

Bake uncovered for 25–30 minutes, or until the top is golden and crispy and the cheese is bubbling.

Let cool for 5–10 minutes before serving.

Tips for Success

• Use good-quality cheese for maximum flavor.

• Warm the milk before adding to prevent clumping.

• Don’t overcook the pasta – al dente is key.

• Add-ins are welcome – try crumbled bacon, roasted garlic, spinach, or even jalapeños.

• Make it gluten-free by using GF flour and pasta.

Make-Ahead and Storage Tips

• Make-Ahead: Assemble the casserole and refrigerate, unbaked, for up to 24 hours. Let it sit at room temp for 30 minutes before baking.

• Freeze: Freeze unbaked or baked for up to 3 months. Thaw overnight in the fridge and bake or reheat.

• Store: Leftovers keep in the fridge for up to 5 days. Reheat in the oven or microwave.

Fun Variations to Try

• Buffalo Mac: Add buffalo sauce and crumbled blue cheese.

• Tex-Mex: Mix in taco meat, black beans, and sprinkle with pepper jack.

• Green Goddess: Add steamed broccoli, peas, or kale.

• Breakfast Bake: Stir in crumbled sausage and top with an egg before baking.

Frequently Asked Questions

Can I use sourdough discard instead of starter?

Yes! Discard works great and adds the same delicious tang without needing to be active.

What if I don’t have sourdough breadcrumbs?

You can use panko or any dry breadcrumbs, but homemade sourdough crumbs offer the best flavor.

Can I use non-dairy milk?

Yes, though whole milk gives the creamiest result. Use a thicker milk alternative like oat or cashew.

Can I add meat?

Definitely. Bacon, ground beef, or shredded chicken all make excellent additions.

Is it kid-friendly?

Absolutely. Kids love the creamy texture and cheesy flavor. You can even hide some veggies inside.

Final Thoughts

This baked sourdough mac & cheese casserole takes everything you love about mac and cheese and gives it a little extra soul. The sourdough starter or discard adds flavor and richness to the sauce, and those crispy sourdough breadcrumbs on top? Pure bliss.

Whether you’re cooking for your family, hosting a gathering, or just need something cheesy and comforting, this dish will hit the spot. It’s hearty, homemade, and easily adaptable to your favorite add-ins.

So the next time your starter is begging to be used, skip the loaf and bake this unforgettable mac and cheese casserole instead.