For the Crust:
1. Preheat your oven to 350°F (175°C). Grease a 12-cup muffin tin or line with paper cupcake liners.
2. In a bowl, combine the crushed digestive biscuits, melted butter, and brown sugar. Mix until everything is evenly combined and the crumbs are moist.
3. Spoon about 1 tablespoon of the biscuit mixture into each muffin tin, pressing it down firmly to form a compact, even base.
4. Bake the crust for 8-10 minutes, or until slightly golden and firm. Once done, remove from the oven and let it cool slightly while you prepare the filling.

1. For the Filling:
   1. In a medium saucepan over low heat, melt the butter, brown sugar, and golden syrup together, stirring occasionally until the mixture is smooth and well combined.
   2. Once the butter mixture has melted, add the ground ginger, cinnamon, and cloves, and stir to combine.
   3. Remove the saucepan from the heat and allow it to cool slightly. Once cooled, whisk in the beaten egg until fully incorporated.
   4. Pour the ginger mixture into the baked crusts, filling each muffin cup about 3/4 of the way full.
   5. Return the muffin tin to the oven and bake for 12-15 minutes, or until the filling is set and slightly firm to the touch. The tarts should still have a slight jiggle in the center when you remove them from the oven.
2. For the Crunch Topping:
   1. While the tarts are baking, melt the dark chocolate and butter together in a heatproof bowl over a double boiler or in the microwave in 20-second intervals, stirring in between, until fully melted and smooth.
   2. Once the tarts are baked and the filling is set, remove them from the oven and drizzle the melted chocolate over the top of each tart.
   3. Use a spoon or spatula to spread the chocolate evenly over the top, creating a thin, glossy layer.
3. Final Steps:
   1. Allow the tarts to cool completely in the muffin tin before transferring them to a wire rack.
   2. Once cooled, carefully remove the tarts from the muffin tin. If you used paper liners, this should be easy; if not, you can gently run a knife around the edges to loosen them.
   3. Serve the tarts chilled or at room temperature.