Preheat the oven to 200 °C / 390 °F or fan-assisted oven to 190 °C / 375 °F. Line a 25 cm x 30 cm or 9-inch x 13-inch baking sheet with parchment paper.
Prepare the puff pastry
Unroll the puff pastry and trim it to a 30 cm x 35 cm (12-inch x 14-inch) rectangle. Place onto the prepared baking sheet. Roll the edges of the pastry inwards, so that the rectangle fits the baking sheet. Using a fork, prick the dough all over, leaving out the edges.TipAlways work with cold pastry, straight from the fridge.
Bake the puff pastry with cream cheese
Brush the center of the dough (leaving out the edges) with olive oil. In a small bowl, stir to combine the cream cheese, mascarpone, lemon zest, garlic powder, and olive oil. Season to taste with salt, and pepper. Spread the cream cheese filling over the pricked pastry. Place in the preheated oven on the lowest rack. Bake for 10 minutes at 200 °C / 390 °F or fan-assisted oven at 190 °C / 375 °F.
Prepare the asparagus
Clean the asparagus and chop off the wooden ends. Discard the woody ends or use them in a vegetable broth. Place the asparagus on a large plate. Season with salt. and pepper and drizzle with a teaspoon of olive oil. Take the tart out from the oven, and arrange the fresh asparagus on top. Place back in the oven on the second rack and bake for 15 - 20 minutes, or until the pastry is beautifully golden-brown.
bake the prosciutto
Line a baking sheet with parchment paper. Arrange prosciutto slices in a single layer over the baking sheet, then place another layer of parchment paper on top of the slices. Cover with another baking sheet. Place in the oven at the same time as you're baking the tart. Place on the lowest rack and bake for 15 - 18 minutes. If the prosciutto isn't crunchy yet, carefully remove the upper baking sheet and parchment paper. Transfer the baking sheet with the prosciutto on the highest rack in the oven and continue to bake for 3 minutes or until golden brown.
Remove the baked Asparagus Tart from the oven. Tear the baked prosciutto on top of the tart and use a speed peeler to freshly shave some parmesan over the tart. Season with pepper and drizzle with olive oil then cut in six slices and serve.