1 pound fresh asparagus, trimmed and cut into 2-inch pieces
6 large eggs
1 cup biscuit/baking mix
1 cup 2% milk
1 cup heavy whipping cream
3/4 cup shredded sharp cheddar cheese
1/2 cup grated Romano cheese
1 teaspoon ground mustard
1 teaspoon dried parsley flakes
1/2 teaspoon salt
1/4 teaspoon pepper
In a large skillet, cook bacon over medium heat until crisp, stirring occasionally. Remove with a slotted spoon; drain on paper towels. Discard drippings, reserving 1 tablespoon in pan.
Add mushrooms and shallot to drippings; cook and stir over medium-high heat until tender, 6-8 minutes. Meanwhile, in a large saucepan, place steamer basket over 1 in. of water. Place asparagus in basket. Bring water to a boil. Reduce heat to maintain a simmer; steam, covered, until crisp-tender, 3-5 minutes.
In a large bowl, whisk eggs, biscuit mix, milk, cream, cheeses and seasonings until blended. Stir in bacon and mushroom mixture. Pour into a greased 13×9-in. baking dish; arrange asparagus over top. Cover and refrigerate overnight.
Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake, uncovered, until golden brown and a knife inserted near the center comes out clean, 30-35 minutes. Let stand 10 minutes before cutting.