Let shredded cheeses stand at room temperature for 30 minutes. Toss cheeses with flour; set aside.
Meanwhile, to toast the bread cubes, place on a baking sheet and bake in a 350 degreee F oven for 5 to 7 minutes or until crisp and toasted; set aside. To precook broccoli or cauliflower, in a saucepan bring a small amount of water to boiling; add florets. Simmer, covered, about 3 minutes or until crisp-tender. Drain and rinse with cold water; set aside.
In a large saucepan heat wine over medium heat until small bubbles rise to the surface. Just before wine boils, reduce heat to low and stir in the cheese mixture, a little at a time, stirring constantly and making sure cheese is melted before adding more. Stir until the mixture bubbles gently.
Stir in milk, kirsch, nutmeg, and white pepper. Transfer cheese mixture to a fondue pot. Keep mixture bubbling gently over a fondue burner. (If mixture becomes too thick, stir in a little more milk.) If desired, sprinkle with paprika. Serve with toasted bread cubes and/or florets.