Step 1

Preheat the oven to 400˚. Combine the squash and onion on a large tray. Drizzle with olive oil, and sprinkle with the salt and black pepper. Toss well to combine. Cook for 25 minutes, until the squash is slightly softened and has released its liquid. Drain the mixture through a colander. Press gently with paper towels to soak up any extra moisture. Let cool.

Step 2

Reduce the oven temperature to 350˚. Place the eggs in a large bowl and whisk. Add the sour cream, mayonnaise, cheddar cheese, and thyme and stir together. Gently fold in the squash and onions (they can still be warm when you fold them in, just be sure they're not piping hot). Transfer the mixture to a lightly-greased three-quart baking dish. Cover and bake for 20 minutes.

Step 3

Combine the melted butter, cracker pieces, and parmesan cheese in a small bowl. Sprinkle in an even layer all over the top of the casserole.

Step 4

Return to the oven for 25 to 30 minutes more, until the crackers are golden brown and the edges are bubbly. Let rest for 10 minutes before serving.