Step 1

Saute onion in oil until tender. Set aside to cool.

Step 2

Mix half and half and cream cheese with a mixer until creamy. Add spinach, cayenne pepper, nutmeg, kosher salt, 1/2 cup sharp cheddar cheese, 1/2 cup Asiago cheese and sautéed onions. Mix well.

Step 3

Pour into a 9 inch buttered casserole dish. Mix together remaining cheese and spread over casserole.

Step 4

Bake at 350 degrees for 45 minutes or until casserole is bubbling and top browns.