Baked Summer Squash Gratin

Yesterday at the grocery store I was picking up excellent local-grown yellow squash.  As I was selecting my squash, a woman described to me, unsolicited, a recipe she had just made with squash and tomatoes.  She said she found it 'on the internet' somewhere.  It sounded wonderful.

I improvised with a sweet and savory stuffing in the middle, and have to say thank you to that stranger, whoever she may be, for sharing her success.  I can only hope she sees this blog!

1 large sweet onion, sliced
1 Tbsp butter plus 1 Tbsp olive oil

2 yellow summer squash, sliced 1/8-inch
2 green zucchini, sliced 1/8 inch
4 plum tomatoes, sliced 1/8 inch
1 small can mushrooms, drained
1/3 cup corn kernels (thawed, if frozen)
1/4 cup golden raisins, coarsely chopped
1 clove garlic, minced
1 Tbsp fresh thyme sprigs
1/2 cup Panko bread crumbs, plus a dash

Make sure your squash and tomatoes are sliced and at the ready.

Preheat oven to 375F. Oil a medium casserole or gratin dish (ideally oval, but not necessary). Alternate the squash and tomato slices in the dish to arrange a single loop around the casserole. You should use about 30 slices of each. Reserve remaining (about 1/4 of the slices) of each squash and tomato, for the filling. Coarsely chop the reserved veggies. You should have about 1-1/2 to 2 cups leftover squash and tomatoes.

Toss the onion in a skillet with the butter and oil and start browning over medium heat, stirring often. Cook for about 15-20 minutes, over low heat, stirring often, to caramelize the onions and develop their flavor.
Meanwhile, tip the reserved squash and tomato into a skillet with a dash of olive oil. Salt and pepper to taste.

Sauté for about 5 minutes and then add the corn and raisins.

Cook for about 5 more minutes and then add the thyme and garlic.

Cook an additional 2-3 minutes and then add the mushrooms.

Cook an additional 3-5 minutes then stir in the panko bread crumbs.

Now assemble the gratin. Stir together the sautéed filling and place in center of gratin. Scatter dash of additional Panko crumbs about the dish and spray with oil.

Bake for about 30-40 minutes, until the gratin is browned and bubbly.

Serves 4-6 as a side dish.