Step 1

Slice the yellow summer squash into roughly 1/4-inch slices, dice the onion. Preheat a medium pan. Add oil or butter to the pan for cooking Add the yellow squash, onions, and garlic. Salt and pepper to taste. Cook about 5 to 7 minutes until slightly softened but still firm. Remove to a colander to drain excess liquid from squash mixture.

Step 2

Combine in a bowl the mayonnaise, milk, and cheese. Salt and pepper to taste.

Step 3

Grease your casserole dish. Add the squash and cheese mixture together into the casserole dish then mix well.

Step 4

Combine the panko breadcrumbs, and additional Parmesan cheese. Top the squash casserole evenly with the topping.

Step 5

Bake in a preheated 400-degree oven for thirty minutes until top is browned.

Step 6

Serve immediately. May be stored for up to one week in an airtight container.