1/2 cup Whole Wild Rice
12 Large Baby Portabella Caps (Mine Were 2 1/2 To 3 Inches In Diameter Before Cooking)
1-1/4 cup Prepared Mashed Potatoes, Preferably Firm (Packaged Works Well Too)
1 Tablespoon Unsalted Butter
2 cloves (Large) Garlic, Minced
1/4 cup Finely Chopped Yellow Onion
2 teaspoons Finely Chopped Fresh Thyme, Plus More For Garnish
1 teaspoon Finely Chopped Fresh Rosemary
1/2 teaspoon Kosher Salt
1/4 teaspoon Black Pepper
1 cup Shredded White Cheddar Cheese, Plus More For Topping
1/4 cup Grated Parmesan Cheese, Plus More For Topping