Directions
Preheat your oven to 375°F (190°C). Lightly grease a baking dish with butter.
Arrange half of the sliced zucchinis and yellow squashes in an even layer in the baking dish. Sprinkle half of the sliced onions and minced garlic over the vegetables. Season with salt, pepper, and a bit of thyme.
Repeat the layers with the remaining zucchinis, yellow squashes, onions, and garlic. Season again with salt, pepper, and thyme.
In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer. Pour the hot cream evenly over the layered vegetables.
Sprinkle half of the Parmesan and Gruyere cheeses over the top of the vegetables.
In a small bowl, mix together the breadcrumbs and the remaining cheeses. Spread the breadcrumb mixture evenly over the top.
Dot the top with the butter, cut into small pieces.
Cover the dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and continue baking for another 15-20 minutes, or until the top is golden brown and the vegetables are tender.
Allow the gratin to rest for a few minutes before serving. Enjoy warm.
Variations & Tips
For a healthier option, you can use low-fat milk or half-and-half in place of heavy cream. For added flavor, consider incorporating other herbs like rosemary or basil. A sprinkle of nutmeg in the cream mixture can introduce a lovely, aromatic note. If you’re a fan of different cheeses, try a mix of mozzarella and cheddar. For a gluten-free version, substitute the breadcrumbs with gluten-free crackers or omit them entirely.
