Kosher salt and freshly cracked black pepper (to taste)
Preheat the oven to 450ºF. Line a baking sheet with aluminum foil.
In a large bowl, toss together the tomatoes, garlic, thyme, olive oil, salt and pepper. Spread out evenly onto the prepared baking sheet.
Bake for 10-12 minutes or until tomatoes slightly charred. Set aside to cool slightly.
Reduce the heat in oven to 350ºF.
Butter a 9×13-inch casserole dish. In a large bowl, add the eggs, milk and mustard. Whisk until blended. Fold in the gruyere, shredded potatoes, and oven roasted tomatoes. Season with salt and pepper. Pour the mixture into the buttered casserole dish.
Place in oven for 35-40 minutes. Let rest for 5 minutes before serving.
Tip: This casserole can be assembled and refrigerated 24 hours in advance.
rry tomatoes (cut in half)