On work surface, brush pastry rounds evenly with mustard. Cut each round into 8 triangles.
Place frozen Mozzarella Stick and sausage at wide end of each pastry triangle and roll up. Place on parchment paper–lined baking sheet, about 2 inches apart.
Beat egg with 1 tbsp water; brush over rolls. Bake in preheated 400°F oven for about 20 minutes or until golden brown.
Tip: Serve with warm tomato sauce or red pepper jelly for dipping.