Cut 4 zucchini and 4 yellow squash in half lengthwise and scoop out the seeds.

Sprinkle the scooped zucchini and squash with kosher salt and place them upside down on paper towels to drain for 30 minutes.

Finely chop the remaining zucchini and yellow squash.

Preheat oven to 350 degrees F (175 degrees C).

Lightly grease a sheet pan.

Heat 1 tablespoon of olive oil in a skillet.

Add shallots and cook until translucent (about 2 minutes).

Add mushrooms and 1/2 teaspoon of salt; cook, stirring, until browned and liquid evaporates (8-10 minutes).

Transfer mushroom mixture to a large mixing bowl.

Sauté chopped zucchini and yellow squash with more olive oil and another 1/2 teaspoon salt until lightly browned and no liquid remains.

Add sautéed squash to the mushroom mixture.

Sauté sausage in the pan until browned.

Transfer sausage to a food processor and process until very fine.

Add sausage to the vegetable mixture with breadcrumbs, cheese, and parsley; mix well and season with salt and pepper to taste.

Fill the zucchini and squash shells with the mixture, sprinkle with extra cheese.

Add 3 tablespoons of water to the sheet pan.

Bake at 350 degrees F (175 degrees C) for 25-30 minutes.

Serve with rice pilaf.