Sauté leeks with 2 Tbsp oil over medium heat until translucent, about 4 minutes. Add thyme, stock, and sprinkle with salt and pepper. Cover, and simmer until leeks are tender and almost all of the liquid is evaporated, about 15 minutes. Allow to cool slightly then transfer mixture to a bowl, and stir in sour cream, cheese, and parsley.

While leeks are cooking, broil asparagus: place in a baking dish, drizzle with 1 Tbsp olive oil, sprinkle with salt and pepper, and toss with balsamic vinegar. Broil for 8 minutes. Set aside.

In another pan, sauté mushrooms with butter and a bit of salt and pepper. Fry mushrooms until soft and moisture is released. Set aside.

Roll out puff pastry or pie crust ¼” thick and into a 10x12” rectangle, then place on a parchment lined baking sheet.

Spread leek mixture to within 1 inch of edge, top with asparagus spears, and roll crust up a bit to form an edge. Bake at 400°F for 15 minutes. Add mushrooms then return to oven for another 5-15 minutes or until crust is golden and fully cooked (depending how thick you made the crust).

Let stand 5 to 10 minutes, then use a pizza wheel to cut into 6-8 pieces.