1.To make the white chocolate ganache, bring the cream to the boil in a medium saucepan; remove from the heat. Add the chocolate and stir until smooth. Refrigerate, stirring occasionally, for about 30 minutes or until thick and spreadable. Add coffee granules to the cream while heating; stir until smooth.
2.Trim cake to tidy. Secure cake to 22cm (9-inch) round or heart-shaped wooden cake board with a little ganache.
3.Use spatula to spread cake all over with ganache until it is about 1cm thick. Stand cake about 20 minutes or until ganache becomes slightly firmer.
4.Using metal scraper, scrape excess ganache from top and side of cake. Reserve ganache scrapings in a small bowl; cover with plastic wrap.
5.Using a small knife, cut a 2cm deep line right around the cake, 1cm in from edge of cake. Refrigerate cake 3 hours or overnight.
6.Scoop out cake (with ganache) inside the cut line to make a recess in the cake about 2cm deep; discard scrapings.
7.Warm reserved ganache over a small saucepan of simmering water; spread ganache evenly inside the recess, don’t fill the recess with the ganache, just use it to cover the base and sides
8.Trace around base of heart-shaped cake pan onto baking paper to make a template for the chocolate box lid. Turn paper over onto a flat tray.
9.Melt chocolate Melts in a small heatproof bowl over small saucepan of simmering water (don’t let water touch base of bowl).
10.Three-quarters fill piping bag with chocolate, snip end from bag; pipe a thick band of chocolate inside the heart outline. Spread more chocolate in the centre of the heart; stand about 10 minutes or until chocolate is set. Repeat this process using remaining chocolate to make a thick lid; re-melt chocolate as necessary.
11.Turn the block of white chocolate upside down; rub your hand over the chocolate to soften slightly. Drag the blade of the cheese slicer over the flat surface of the chocolate to make curls.
12.Position chocolates in box; sprinkle curls between chocolates.
13.Peel baking paper from the back of the chocolate lid; tie a ribbon around lid, finish with a bow. Place on top of cake.
A cheese slicer makes curls about 2.5cm long; if you don’t have one, use a vegetable peeler, it will make smaller curls. We used a white chocolate mud cake in this recipe, and made a coffee-flavoured ganache to complement it and the chocolates, however, a dark chocolate mud cake would also look wonderful filled with heart-shaped chocolates in red wrappers.