Preheat oven to 425° F.

Trim puff pastry to a 9- by 6-inch rectangle. Lay pastry out on a parchment paper-lined baking sheet. About 1/2 inch from the outer edge, cut a border into the pastry all the way around. (Don’t cut completely through to the work surface.) With a fork, prick the surface of the pastry all over except around the border. This will allow the border to rise and the center to stay less aerated when it bakes. Brush the entire pastry sheet very lightly with the egg wash.

Bake for 5 minutes and allow to cool.

Heat olive oil in a small sauté pan over medium heat and sauté shallots until golden, about 4 minutes. Season with salt and pepper.

If asparagus spears are thicker than your little finger, blanch for 30 seconds in boiling, salted water; refresh in cold water and pat dry. If thin, leave uncooked.

Combine chèvre cheese, cream cheese and thyme and spread on puff pastry; scatter with shallots. Lay asparagus spears side by side on top of shallots and distribute prosciutto over the top. Shave or grate cheese and distribute over the tart. Add any other toppings you prefer.

Bake until the pastry is a deep golden, 9 to 12 minutes. Drizzle with a little olive oil or truffle oil. Garnish with lemon slices and thyme leaves.