How to Make It
Heat oven to 350°F. Place the mushroom, stem-side up, on a small baking sheet, and season with a pinch of salt and pepper. Scatter the pancetta pieces on top, and coat with spray. Place in the oven for 12–15 minutes until the mushroom is softened and the pancetta is golden.
Remove from oven, and top with the cheese and a few drops of Worcestershire sauce. Slide under a medium-hot broiler for 1–2 minutes until the cheese is melting. Garnish with the chopped parsley or chives.