Preheat your oven to 375°F (190°C) and line a large baking sheet with parchment paper.

In a skillet over medium heat, melt 2 1/2 tablespoons of butter. Add the sliced onion along with the chopped rosemary. Cook until soft and lightly golden, about 5-6 minutes. Set the mixture aside to cool.

On a clean work surface, lightly dust with flour and roll out each sheet of puff pastry to about 1/4-inch thickness. Cut out approximately twenty 4-inch circles.

Arrange ten pastry rounds on the baking sheet and prick them all over with a fork to prevent bubbling. Use the remaining rounds to cut out smaller circles to create rings.

Brush the base rounds with the beaten egg, and place a ring on each to form raised edges. Chill the pastry shells in the freezer for 15 minutes.

In a bowl, gently mix the goat cheese with lemon juice, salt, and pepper, maintaining a slightly crumbly texture.

Spoon a small amount of the onion mixture onto each chilled pastry base, followed by about 1 tablespoon of the goat cheese mixture.

Layer the apple and pear slices on top of the cheese, slightly overlapping, and sprinkle with chopped walnuts.

Melt the remaining butter and lightly brush it over the fruit, then sprinkle a pinch of allspice on top.

Bake for 25-30 minutes, or until the pastry is puffed and golden brown.

When ready, drizzle the warm tarts with honey and garnish with fresh herbs if desired. Serve warm or at room temperature.