Adapted from my friend, Kaye
2 tablespoons butter
6 ounces fresh button mushrooms, sliced
10 slices of white sandwich bread, crusts removed (Pepperidge Farm works well)
5 ounces Black Forest ham, cut into 1/2 inch pieces
1 1/2 cups (6 ounces) grated Monterey Jack cheese, divided
1 3/4 cup whole milk (do not use low fat or skim)
1 tablespoon chopped fresh thyme
1 teaspoon dry mustard
1/4-1/2 teaspoon salt (depends on saltiness of ham)
1/4 teaspoon freshly ground black pepper
Saute mushrooms in butter till golden. Season lightly with salt and pepper.
Butter an 8 x 8 inch baking dish (use a 9 x 13 to double recipe). Line the bottom with half the bread slices, trimming to fit. Top with ham, then sprinkle with one cup of the grated cheese (the remaining 1/2 cup will be added before baking), followed by the mushrooms. Add enough of the remaining bread to cover the filling with one layer. Whisk the eggs, milk, half the thyme, mustard, salt and pepper till well blended. Pour over bread. Cover and refrigerate overnight.
The next morning, preheat the oven to 350º. Bake uncovered till puffed and lightly browned, about 1 hour. Mix remaining cheese and thyme and sprinkle over casserole. Return to oven for about 3 minutes or till the cheese melts. Let sit 10 minutes before serving.