Preheat oven to 400.  On a floured cutting board, roll out your puff pastry into a rectangle shape aoproximately 11″ X 14″. Be careful not to tear the pastry. (if you do “patch” it with another piece of pastry dough) Transfer puff pastry to a parchment lined sheet pan. Prick the pastry dough all over with a fork. Roll the edges of the pastry dough over one time so you have a 1/2″ edge and prick the edges as well. Gently brush mustard over bottom, leaving a 1″ border. Sprinkle gruyere and romano cheeses – again leaving the 1″ edge. Arrange asparagus spears either diagonally or horizontally so that tips are all in the same position. Scatter sliced shallot and lemon zest evenly over asparagus and garlic (if using garlic). Drizzle with a little olive oil (just a few tablespoons). Sprinkle on salt and pepper and thyme sprigs.  Brush edges with egg wash. Bake for 20-25 minutes or until the crust is golden brown and edges are puffed a bit.  Let cool for 5-10 minutes before slicing. Garnish with more thyme. We like to slice this into squares and often top with organic mixed greens tossed with olive oil, lemon and salt