Preheat oven to 425 degrees.
Fit a quarter sheet pan with parchment.
Using a pizza cutter, or a flouted pastry cutter, divide thepuff pastry into 4 pieces.
Spread dijon over the puff pastry pieces.
Going corner to corner, divide asparagus, bacon, tomatoes, onion, and gruyere between the puff pastry squares.
Wrap 2 edges of the puff pastry around the asparagus, and press to seal.
Wrap 2 edges of the puff pastry around the asparagus, andpress to seal.
Brush the egg mixture on the bundles.
Bake for 12-15 minutes, or until golden brown and the cheese has melted.
Serve immediately.