4 Tbsp (1/2 stick) butter
2-1/2 lbs asparagus, trimmed and cut into 1-inch pieces
1 (8-oz) package white mushrooms, sliced
1/2 medium sweet onion, chopped
1/4 Cup all-purpose flour
1-1/4 Cup milk
1/2 Cup mayonnaise
1/2 Cup sour cream
1/2 Cup shredded cheddar cheese
1/2 Cup shredded swiss cheese
1/2 tsp Kosher Salt
1/2 tsp Lemon Pepper
1/4 tsp Paprika, Smoked Bittersweet
1 (6-ounce) can french-fried onions.
Preheat oven to 350°F.
In a large skillet or sauté pan, melt butter over medium heat. Add the asparagus pieces, sliced mushrooms, and chopped onions. Sauté the vegetables for about six minutes, stirring once or twice as they brown and soften. Sprinkle the quarter-cup of flour over the vegetables, tossing to coat, and cook mixture for another minute, stirring continuously.
Gradually add the milk to the vegetable mixture. Bring mixture to a near-boil, then reduce heat to a bare simmer, and let the mixture bubble until thickened. Reduce heat to low and stir in the mayonnaise, sour cream, shredded cheeses, and spices, stirring after each addition to fully incorporate ingredients. Remove pan from heat.
Pour about one-third of the canned fried onions into a resealable sandwich bag, close, and crush crispy onions before emptying bag over the pan, stirring into the mixture. Pour vegetable mixture into an oiled casserole or baking dish, and sprinkle remaining onions on top before popping into the oven. Bake 30 minutes, or until casserole is heated through and top of dish is golden brown.
Remove from oven and allow to cool 5-10 minutes before serving.