I got this recipe from a co-worker several years ago. I changed a few of the original ingredients and added a few extras of my own. This is a great sunday side dish that can be made a day ahead and refridgerated. I love recipes that I can prepare ahead when I have company coming for dinner. It allows me to spend time visiting and not worrying about preparation of a meal.Plus this recipe is yummy!
Bake the potatoes in a 375 degree oven until tender. Set aside until cool enough to handle. When cool, cut the potatoes in halves length wise and scoop pulp into a mixing bowl.
Melt 1 stick of butter in a skillet. When the butter is melted, add the onions and saute until clear or soft (about 10 minutes).
Add prosciutto, and drained spinach to the onion mixture. Cook another 5 minutes.
Turn off heat and add parmesan cheese to the onion mixture. Stir till well blended.
Add 1/2 stick butter, hot milk, and sour cream to the potatoe pulp. Add salt and pepper to taste and mash well.
Stir in the onion/spinach mixture (combine well).
Pour mixture into a well greased/buttered baking dish (one that has a lid) and smooth the top.
Sprinkle the top lightly with salt and pepper. Scatter the grated cheese on top. Cover with a buttered baking lid and set aside till ready to bake If refridgerated, bring casserole to room temperature before baking).
Bake the covered casserole at 375 degrees for 30 minutes. Uncover and bake another 15 minutes. Remove from oveb and serve hot.