It's best to use good-quality dark chocolate with at least 70% cocoa solids for cooking, but you can use milk chocolate if you prefer.

To melt chocolate, chop it, then place in a dry, heatproof bowl over a pan of simmering (not boiling) water. The bowl shouldn't touch the water. As the chocolate melts, stir very gently with a wooden or metal spoon to ensure it melts evenly. As soon as the chocolate is smooth, remove the bowl from the heat. If the chocolate overheats, or if water is in contact with it as it's melting, it will 'seize' and become hard and unusable.

Storing the cake: Cool cake completely before storing in an airtight container. Keep un-iced cake at room temperature for up to 2-3 days. You can freeze any leftover cake in plastic wrap for up to 6 months. To defrost, thaw out in the fridge, then at room temperature.

Variations

Soft-centred chocolate puddings: Preheat the oven to 180°C. Grease eight 200ml ramekins. Omit the cocoa, baking powder, bicarbonate of soda and milk from the master recipe above, reduce the plain flour to 50g, and replace the caster sugar with 1/2 firmly packed cup (100g) brown sugar. Make a batter as per the master recipe method, adding the flour all at once rather than in stages. Spoon the mixture into the ramekins. Bake in the oven for 12-15 minutes until set on the surface but still slightly soft in the centre. Remove from the oven, dust with icing sugar and serve immediately with thick cream.

Choc-macadamia ice cream layer cake: Halve all the quantities for the master recipe, then make the cake as per the master recipe method, instead using a greased and lined 7cm-deep, 25cm x 10cm loaf pan. Cool as for the master recipe, then carefully cut a thin layer from the top of the cake and discard. Slice the remaining cake horizontally into 3 long pieces. Place cake slices on a tray, with plastic wrap or baking paper between each layer, and freeze for at least 1 hour. Clean loaf pan, then line with plastic wrap, leaving enough overhanging to cover the top. Return bottom layer of cake to pan. Working quickly, use a hot palette knife (dip it in hot water) to evenly spread about 1 1/2 cups ice cream (we used macadamia) over the cake, right to the edges. Repeat with another layer of cake and ice cream, then top with remaining piece of cake. Cover with overhanging plastic, then freeze for at least 3 hours. Remove cake from pan, using plastic wrap to help, then cut into 6-8 slices. Serve drizzled with chocolate sauce, if desired.

Chocolate & hazelnut petits fours: Halve all the quantities for the master recipe, then make the cake as per master recipe method, instead using a greased and lined 7cm-deep, 25cm x 10cm loaf pan. Carefully slice cooled cake in half horizontally. Cut each piece into 3 long strips, then cut each strip into 8 pieces to make 48 cubes. Set aside. To make chocolate icing, place 100g chopped good-quality dark chocolate, 60g unsalted butter and 3 tbs water in a heatproof bowl set over a pan of barely simmering water (don't let bowl touch the water) until chocolate melts. Stir in 1/2 cup (75g) sifted icing sugar, then remove bowl from heat and cool slightly. You should have a thin, glossy icing - add a little water if too thick. Place cakes on a rack. Top each with 1/4 tsp Nutella (or other hazelnut spread). Gently press in a hazelnut or macadamia. Using a small palette knife, drizzle and spread icing over cakes. Sprinkle with flaked chocolate garnish (from supermarket baking aisle), then leave to set at room temperature for at least 2 hours.