Preheat your oven to 400 degrees F, and line a large baking sheet with parchment paper.
Roll your puff pastry out on a lightly-floured surface to a 16x12in rectangle (or something similar - it doesn't have to be perfect). Brush the edge with the egg wash (about 1 inch from the edge). Sprinkle with salt. Bake the puff pastry for about 10 minutes or until just lightly brown and starting to puff.
Meanwhile in a large skillet, bring about an inch of water to a boil. Add the asparagus, and cook covered for about 5 minutes or until bright green. Remove the asparagus from the pan, and pat dry with a paper towel. Set aside.
Sprinkle the partially cooked puff pastry with 1/2 cup of fontina cheese and 1/2 cup of gruyere. Lay the asparagus on top, and then sprinkle on the remaining cheeses. Add the prosciutto in small clumps, and then drizzle the entire thing with olive oil. Bake for about 10-15 minutes more, or until the cheese is melted.
Add the burrata and soft or hard-boiled eggs. Serve immediately with hot honey (recipe below).
To make the hot honey, simply whisk together the honey, crushed red pepper, and hot sauce. Drizzle on top of the tart.