Make the Herb Butter: In a mixing bowl, combine the softened butter, parsley, thyme, rosemary, lemon zest, garlic, salt, and pepper. Mix until well incorporated. You can use a fork or spatula to achieve a smooth consistency.
Prepare the Pastry: Preheat your oven to 400°F (200°C). Roll out the puff pastry on a lightly floured surface to about 0.25 inches thick. Cut into squares (4x4 inches) or circles, depending on your preference.
Assemble the Tarts: Place the pastry squares onto a parchment-lined baking sheet. Using a knife, gently score a smaller square or circle inside each piece, about 0.5 inches from the edges, being careful not to cut all the way through. This will create a border for the filling.
Spread the Filling: In a small bowl, mix the ricotta cheese with Parmesan cheese. Spoon the cheese mixture into the center of each pastry, avoiding the scored edges. Then, generously dollop a portion of the herb butter on top of the cheese filling.
Apply Egg Wash: Brush the edges of the pastry with the beaten egg for a beautiful golden color after baking.
Bake: Place the tarts in the preheated oven and bake for 15-20 minutes, or until the pastry is golden brown and puffed.
Garnish and Serve: Once out of the oven, let the tarts cool slightly. Garnish with additional fresh herbs if desired. Serve warm as an appetizer or snack.