Asparagus, Prosciutto and Fontina Tart

Thaw the pastry sheet at room temperature for 40 minutes or until it's easy to handle. Heat the oven to 400 degrees F. Line a baking sheet with parchment paper. Unfold the pastry sheet on a lightly floured surface. Roll the pastry sheet into a 10 x 14-inch rectangle. Place the pastry sheet onto the baking sheet. Brush the pastry sheet with the mustard. Fold in the edges of the rectangle about 1/4-inch and crimp with a fork to seal. Arrange the asparagus on the pastry in a single layer. Sprinkle with the prosciutto, fontina and thyme. Bake for 20 minutes or until the pastry is golden and the asparagus is tender.