Mix Gruyere cheese and panko bread crumbs together in a bowl.
Heat butter in a large skillet over medium heat until melted. Add zucchini, yellow squash, shallots, and garlic; cook and stir until softened, about 10 minutes. Stir in basil, rosemary, salt, and black pepper; cook until fragrant, about 1 minute.
Mix flour into the skillet. Pour in cream in a steady stream and stir until thickened, 3 to 5 minutes. Mix in half the cheese mixture. Remove from heat.
Pour zucchini mixture into a baking dish. Top with remaining cheese mixture.
Bake in the preheated oven until bubbly and golden brown, about 20 minutes.
Use green or yellow squash, or both.
358.46 calories; 15.28 g protein; 22.74 g carbohydrates; 1.03 g dietary-fiber; 2.53 g sugars; 25.54 g fat; 15.9 g saturated-fat; 77.55 mg cholesterol; 1167.96 IU vitamin-a-iu; 3.38 mg niacin-equivalents; 0.27 mg vitamin-b6; 14.19 mg vitamin-c; 34.37 mcg folate; 373.39 mg calcium; 0.69 mg iron; 35.46 mg magnesium; 323.09 mg potassium; 265.22 mg sodium; 0.09 mg thiamin; 229.89 calories-from-fat; 23 percent-of-calories-from-carbs; 60 percent-of-calories-from-fat; 16 percent-of-calories-from-protein; 37 percent-of-calories-from-sat-fat
This is absolutely delicious. Don't change a thing. The rosemary and basil and gruyere make this so elegant. Congrats to the chef!!! And thank you for sharing your recipe. I took this to a dinner party and everyone loved it and the hostess asked for the recipe.