Reinvent the popular deli sandwich into this melty, salty, tangy creation. Baking the pizza on the bottom rack ensures a crisp golden crust.
Heat oil in small saucepan over medium heat. Add onions and cook until softened, about 2 minutes. Sprinkle with flour and cook, stirring. Stir in warm milk. Cook, stirring, until thickened, about 5 minutes. Stir in nutmeg, salt, pepper and mustard. Transfer to small bowl, cover with plastic wrap and cool for 20 minutes.
On lightly floured surface, roll out pizza dough to 14-inch circle. Transfer to greased 15-inch pizza pan. Spread béchamel over dough leaving a 1-inch border at edge of crust. Sprinkle with 1 cup of the mozzarella cheese. Bake on bottom rack of 425ºF for 20 minutes. Top with Montreal smoked meat, pickles and remaining mozzarella. Bake at 425ºF for 3 minutes or until cheese is melted. Slice into 8 pieces. Drizzle with mustard, if desired.