Step 1: Begin by melting the butter in a saucepan over high heat. Add the leeks, salt and pepper and sauté for 3 minutes. Stir in water and cook until water has evaporated.
Step 2: Stir in the heavy cream and cook until reduced by half. The sauce should appear rich and creamy. Fold in the parmesan cheese. Set aside.
Step 3: Next, coarsely chop the assorted mushrooms and mix with 3 tablespoons oil, thyme, and salt and pepper. Toss to coat the mushrooms evenly.
Step 4: Evenly arrange the mushrooms in a single layer on a rimmed baking sheet. Bake in a 450°F oven until just beginning to colour (about 10 minutes).
Step 5: In a cup, whisk together garlic, balsamic vinegar, chives, mustard and the remaining oil. Toss into mushroom mixture to coat.
Step 6: Divide the leek mixture over English Muffin halves and top with the roasted mushrooms. Garnish the dish with pea shoots or Gouda (if desired).