These Mini Roasted Beef and Gruyère Savory Tarts are a delightful combination of flaky puff pastry, tender roast beef, and rich Gruyère cheese, perfect for any occasion from brunch to dinner.
1 sheet puff pastry (thawed)
1/2 cup sour cream, 1 teaspoon Dijon mustard, 1 teaspoon horseradish (optional)
1 cup cooked roast beef (thinly sliced or chopped), 3/4 cup shredded Gruyère cheese, 1 small red onion (thinly sliced), 1 tablespoon olive oil, 1/2 teaspoon fresh thyme leaves, salt and black pepper to taste, 1 egg (beaten, for egg wash), chopped fresh parsley for garnish