5 eggs
1 tbsp Dijon mustard
2 tbsp thick sour cream or creme fraiche (or sub with mayonnaise)
⅔ cup grated gruyere cheese, separated (2 x ⅓ cup) (or any other melting cheese)
Salt and pepper
1 sheet store bought frozen puff pastry, thawed (25 cm x 25cm / 10″ x 10″)
1 tbsp butter (salted or unsalted)
5 oz / 150g mushrooms, sliced (approximately 2 cups of sliced mushrooms)
6 – 8 oz / 200 – 250 g bacon, roughly chopped