1 hour before assembly- mix tomato, onion and vinaigrette.
Thaw frozen puff pastry at room temperature for 20 to 30 minutes. Preheat oven to 400 degrees. Cut pastry into 4 inch squares.
Fry sausages until cooked through. Cut into 1 ½ inch pieces. Place a sausage chunk with one teaspoon of tomato mixture in the middle of a 4 inch square of puff pastry. Dip finger into warm water and wet the edges of the square. Gather corners up to form a “purse” and squeeze to close. Repeat with remaining sausage. Brush with beaten egg. Bake at 400 degrees for 12 to 15 minutes until golden and heated through. Serve with Irish whole grain mustard.