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

In a skillet over medium heat, melt 2 ½ tablespoons of butter. Add the sliced onion and rosemary, then cook until they are golden, about 5–6 minutes. Set aside to cool.

Lightly flour a clean work surface and roll out the puff pastry to about 1/4-inch thickness. Cut out roughly twenty 4-inch circles.

Arrange ten pastry rounds on the baking sheet and prick them with a fork to prevent puffing too much. From the remaining rounds, cut out smaller circles to create rings for the edges.

Brush the base rounds with beaten egg, then place the rings atop each one to form raised edges. Chill these pastry shells in the freezer for about 15 minutes.

In a bowl, mix the goat cheese with lemon juice, salt, and pepper until just combined.

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

Arrange the apple and pear slices over the cheese, overlapping slightly for a lovely presentation, and sprinkle with the chopped walnuts.

Melt the remaining butter and gently brush it over the fruit, then sprinkle with a touch of allspice to enhance the flavors.

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

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