Preheat oven to 400° F. Coat a rimmed 12 x 16 inch cookie sheet with non-stick spray. Stretch dough into cookie sheet. Cover with plastic wrap and let rest for 10 minutes. Continue to stretch dough so it fills pan, and form a ridge around edge, making a crust. Bake 15 to 20 minutes or until golden brown, and let cool.
Spread mustard onto prebaked tart. Top with sauerkraut, prosciutto and bits
of cheese. Bake 10 minutes, or until cheese is melted. Let cool for 5 to 10
minutes, then cut into squares and serve.