Line a loaf tin (approx. 23 x 11 x 7 cm / 9 x 4 x 3 in) with parchment paper, leaving an overhang on two opposite sides to lift the doorstop out. If you want a sharper ‘doorstop’ wedge shape, use a slightly narrower tin. Measure and have all ingredients ready.

Melt chocolate mixture

Place the chopped dark chocolate, butter and golden syrup in a heatproof bowl. Set the bowl over a pan of barely simmering water (double boiler), ensuring the bowl doesn't touch the water. Stir gently until the chocolate and butter are fully melted and glossy, then remove from heat.

Combine dry ingredients

In a large bowl, combine the crushed digestive biscuits, puffed rice, and toasted chopped hazelnuts (if using). Sprinkle the sea salt flakes over the dry mix and stir to distribute.

Bind the crunch mixture

Pour the melted chocolate mixture over the dry mix. Using a spatula, fold until everything is evenly coated and the texture is sticky but still retains some crunch from the puffed rice. Taste a small piece and adjust salt if necessary.

Shape into doorstop

Spoon the chocolate-crunch mixture into the prepared loaf tin. Press firmly and evenly into the tin with the back of a spoon or the base of a measuring cup to compact the mixture—this ensures the slice will hold together. Smooth the top level. If you want a true doorstop wedge, you can press more at one end to create a slight incline.

Chill to set

Refrigerate the filled tin for at least 1 hour (or 30 minutes in the freezer) until the mixture is fully set and firm to the touch.

Top chocolate coating & finish

Melt milk chocolate

Place the milk chocolate and the teaspoon of oil in a clean heatproof bowl. Melt over a simmering pan of water (or in short bursts in the microwave, stirring every 20 seconds) until smooth and glossy. The oil will thin the coating for a smooth pour.

Unmold and coat

Lift the set base out of the tin using the parchment overhang and place it on a wire rack over a tray to catch drips. Pour the warm milk chocolate evenly over the top, using a spatula to smooth and ensure the sides are coated if desired. Work quickly before the coating sets.

Add final embellishments

While the top chocolate is still wet, sprinkle the extra chopped nuts or crushed biscuits and a small pinch of sea salt across the top for texture contrast. If using, dust lightly with sifted confectioners' sugar for a decorative finish.

Final chill and slice

Return the coated doorstop to the fridge for 15–20 minutes until the top chocolate is set. Remove from the fridge 10 minutes before slicing to ease cutting. Using a sharp knife warmed under hot water and wiped dry between cuts, slice into thick wedges — each wedge resembles a chocolate 'doorstop'. Wipe the knife between each slice for clean edges.

Serve and store

Serve at room temperature for the best texture. Store leftovers in an airtight container in the refrigerator for up to 7 days (allow to come to room temperature before serving), or freeze for up to 1 month.