For onion lovers and beyond, this onion gratin is a great side dish to any meal. The combination of roasted onions, herbs, and cheeses builds a bite full of rich flavor. Makes about 6 servings.
Rosemary and Thyme Onion Gratin
- 8 medium-sized onions, peeled and cut to half-inch thick slices
- 1-2 T olive oil
- 1 tsp. fresh rosemary (or 1/2 tsp. dried rosemary), finely minced
- 2 T fresh thyme leaves (or 1 T dried thyme), minced
- 6 T mayo
- 1 T fresh squeezed lemon juice
- 1/2 tsp. Dijon mustard
- 1 cup mozzarella or mild white cheese
- 3 T Pecorino-Romano cheese or parmesan cheese, grated
- Black pepper to taste
- Preheat oven to 450 F/230 C. Spray or brush baking sheet with olive oil, then arrange onion slices in a single layer. Spray or brush onions with oil, then sprinkle with chopped herbs. Roast onions 15 minutes, then take them out and turn oven down to 375F/190C.
- While onions are roasting, combine mayo, lemon juice, Dijon mustard, cheeses, and black pepper in a small bowl. Mix together with a fork.
- Coat a 9" x 13" casserole dish with olive oil or nonstick spray. Remove baking sheet from the oven and layer onions in the casserole dish. Spread topping over onions. Place casserole dish in oven and bake 25-35 minutes, or until top is golden brown and onions are slightly bubbling. Serve immediately.