Preheat oven to 350°F. Spray a 2 ½ quart casserole dish or 9 x 13-inch baking dish with non-stick spray. Set aside.
Combine ¼ cup of Parmesan cheese and one teaspoon paprika in a small bowl. Set aside.
Melt butter in a large non-stick skillet over medium heat. Add onions; cook for 5 minutes or until tender. Increase heat to medium-high and add mushrooms. Cook, stirring frequently until mushrooms begin to brown, about 3 minutes.
Sprinkle on flour, salt, pepper and garlic powder. Cook for several minutes. Add milk; stir constantly until thick and bubbly. Add ¾ cup of Cheddar cheese; stir until melted. Add ham and green peas; stir to combine.
Add undiluted cream of mushroom soup, ½ cup of grated Parmesan cheese, sherry and drained pimentos. Stir to combine. Add cooked spaghetti; toss to combine.
Transfer tetrazzini mixture to prepared baking dish. Bake uncovered in preheated 350°F oven for 25 minutes or until heated through and bubbly. Remove from oven and top in diagnol rows of parmesan/paprika mixture, shredded cheddar cheese and toasted almonds. Return to oven for 10 additional minutes or until cheeses are melted.
Yield: 8 servings. (See Tip 5)
Tips/Notes
Feel free to use whatever pasta you have on hand. Just make sure to cook it to the al dente stage.
For a richer dish, you can use half and half in place of the milk.
The dry sherry adds a subtle flavor. If desired, you can either omit the sherry, or use white wine in place of it.
To toast the almond slices, bake them at 350°F for 8 to 10 minutes. Watch carefully to ensure that they don't burn.
This makes excellent leftovers, and freezes beautifully.