Southern Yellow Squash Casserole

Why you’ll love it

• Creamy and cheesy inside, with a crunchy, buttery cracker top.
• Simple ingredients you can find in any grocery store.
• Holiday-friendly: assemble it a day ahead and bake when you need it.

Quick facts

Ingredients

For the squash

• 3 lb (1.4 kg) yellow summer squash (about 8 medium), sliced 1/4 inch (6 mm) thick
• 1 medium yellow onion, diced
• 2 tbsp (28 g) unsalted butter
• 1 tsp kosher salt

For the creamy filling

• 2 large eggs
• 1/2 cup (120 g) sour cream
• 1/4 cup (60 g) mayonnaise
• 1/2 tsp black pepper
• 1/4 tsp garlic powder
• 1 1/2 cups (170 g) shredded sharp cheddar cheese, divided

For the cracker topping

• 1 sleeve (about 36 crackers, 4 oz / 115 g) round butter crackers, coarsely crushed
• 3 tbsp (42 g) unsalted butter, melted

Step-by-step method

1. Heat the oven. Heat the oven to 350°F (175°C) with a rack in the center. Butter a 2-quart (2 liter) baking dish, such as an 11×7-inch (28×18 cm) dish.

2. Cook the squash. Melt the 2 tbsp butter in a large, deep skillet or sauté pan over medium heat. Add the onion and cook 3 minutes. Add the squash and salt, stir, cover and cook 10–12 minutes, stirring now and then, until the squash is tender.

3. Cook off the liquid. Uncover and cook 5 minutes more, stirring, so some of the liquid evaporates. Transfer the squash to a colander set in the sink and let it drain 10 minutes, pressing gently with a spatula to release the extra liquid.

4. Mix the filling. In a large bowl, whisk the eggs, sour cream, mayonnaise, pepper and garlic powder until smooth. Fold in the drained squash and 1 cup (115 g) of the cheddar.

5. Assemble. Spread the squash mixture evenly in the baking dish and sprinkle with the remaining 1/2 cup (55 g) cheddar. Toss the crushed crackers with the melted butter and scatter them over the top.

6. Bake. Bake 30–35 minutes, until the casserole is bubbling at the edges, set in the center and the topping is golden brown.

7. Rest and serve. Let the casserole rest 10 minutes before serving, so the filling firms up and slices neatly.

How to know it is done

The casserole is ready when the edges are bubbling, the cracker topping is deep golden and the center no longer looks wet or jiggly when you gently shake the dish. A knife inserted in the center should come out without liquid egg; an instant-read thermometer in the center reads about 160°F (71°C).

Tips for the best result

• Drain the cooked squash very well; squash holds a lot of water, and a soggy filling is the most common problem.
• Choose small to medium squash with smooth, bright skin; they have fewer seeds and a sweeter flavor.
• Shred your own cheddar from a block for the creamiest, smoothest melt.
• Add the cracker topping just before baking so it stays crisp.

Variations and substitutions

• Half zucchini: use 1 1/2 lb (680 g) yellow squash and 1 1/2 lb (680 g) zucchini.
• Lighter: replace the mayonnaise with more sour cream or plain Greek yogurt.
• Different topping: use 1 cup (50 g) panko or crushed cornflakes tossed with the butter instead of crackers.
• With bacon: fold 4 slices of crumbled cooked bacon into the filling.
• Spicy: use pepper Jack instead of cheddar and add a pinch of cayenne.

Make ahead

Cook and drain the squash, mix the filling and spread it in the baking dish up to 1 day ahead; cover and refrigerate. Keep the buttered cracker topping in a separate container. Before baking, let the dish sit at room temperature 20 minutes, add the cheese and topping, and bake 35–40 minutes.

Storage and reheating

Refrigerate leftovers, covered, up to 4 days. Reheat individual portions in the microwave 1–2 minutes, or warm the dish covered with foil in a 350°F (175°C) oven for 15–20 minutes, uncovering for the last 5 minutes to re-crisp the topping. Freezing is not recommended, because the squash turns watery when thawed.