Asparagus Egg and Cheese Casserole

10 large eggs
1/2 tsp olive oil
1 medium onion, chopped
6 asparagus spears, bottoms trimmed, sliced 1/8-inch thin
2 cups grated or shredded cheese (I use Sargento reduced-fat shredded Cheddar, from the supermarket, or any leftover shredded cheese from my freezer.)
2 Tbsp skim milk
1/2 tsp dried thyme leaf
2 tsp chopped fresh flat-leaf parsley
1/2 tsp kosher salt
1/2 tsp fresh black pepper
Cooking spray (canola or olive oil)

Preheat oven to 375°F. Prepare a casserole dish by spraying with cooking spray. In a large bowl, lightly beat the eggs. In a small frying pan, heat the oil, and add the onions and asparagus. Sauté until onions are translucent, 2-3 minutes. Remove the pan from heat and set aside to cool for 2 minutes. Then, mix the onions and asparagus into the eggs along with all of the remaining ingredients. Pour the mixture into the casserole dish. Bake at 375F for 35 minutes, until the casserole is lightly browned and a bit puffy. Remove from the oven and let cool for 5 minutes before eating. 

(Can be made up to one day ahead. Cool, cover and refrigerate. To reheat, uncover and place in a 350F oven for 15-20 minutes.)