Heat 1-inch salted water (1/2 teaspoon salt to 1 cup water) to boiling; add cauliflower. Cover and heat to boiling. Cook until tender, 20 to 25 minutes; drain.
Melt butter in 8-inch skillet over low heat. Stir in flour, mustard, salt and pepper. Cook over low heat, stirring constantly, until mixture is smooth and bubbly. Remove from heat.
Stir in half-and-half and wine (mixture may appear to curdle slightly at first). Heat to boiling, stirring constantly. Boil and stir 1 minute. Stir in cheese. Cook and stir over low heat until cheese is melted. Pour sauce over hot cauliflower. Sprinkle with paprika if desired.