I’ve made this cake once before, following Heidi’s recipe more closely then. That time the cake turned out as she described, thick, dense and fudgey, sunken in the middle and so gooey it had to be eaten with a fork, rather than fingers. I decided to make a few changes this time, not intending to change the end result too much, but more out of convenience. I used a little more chocolate than was called for and considerably less sugar (less than half) – the cake wasn’t noticeably not sweet, leading me to believe that in most recipes sugar is used more for texture than flavour; certainly in many types of biscuit this is true, but I thought it would have less effect in a cake. I also played around with the flours, using teff flour to give it a bit of a nutty flavour and a little more structure, as well as plenty of tapioca starch. To counteract the absorption effect of the tapioca (in some gf recipes you’ll see it substituted for arrowroot or even xanthan gum; it’s very fine and has thickening, stabilising properties) I added in an extra egg too. The result was, well, a completely different chemical composition from the original recipe so I suppose it’s not too surprising that the cake was sturdier (some good binding starches in there), richer (more chocolate and less sugar so a “darker” taste) and didn’t collapse (extra raising agent in the form of an additional egg). The texture was that of a well-made chocolate sponge, springy, with lots of tiny air bubbles, but still sturdy and a little dense from the chocolate. To take it from great to sublime, I would definitely add a couple of handfuls of chocolate chunks to the batter next time.
The base recipe was for a 9×5-inch loaf tin, and of course mine are smaller, at 8×4 inches and I still refuse to buy more when all I need to do is a little bit of maths (or get my muffin trays out), so the recipe below is for an 8×4 tin, and makes 4 mini muffins as well with the batter, or should fit perfectly in a 9×5 tin.
125g medium dark chocolate (60% cocoa), melted
230g (1 cup) butter, softened
100g (1 very, very loosely packed cup) dark brown sugar
1 teaspoon vanilla extract
170g (1 heaped cup) gluten-free flour blend (50% white rice flour, 30% brown teff flour, 20% tapioca starch)
1 teaspoon bicarbonate of soda
1/2 teaspoon salt
250ml boiling water
1. Line your loaf tin with greaseproof paper. Make sure the paper extends a little over the top of the tin, in case the cake expands too much. Preheat the oven to 190 C.
2. Melt the chocolate in a small bowl and set aside. In a large bowl beat the butter and the sugar together until light and fluffy. Add the eggs, one at a time, then the vanilla.
3. Mix the flour with the bicarbonate of soda and the salt. Stir about 1/3 of the flour mixture into the butter/sugar/eggs until fully combined, then stir in about 1/3 of the boiling water. Continue adding the flour, and water until everything is thoroughly mixed in. The batter should be thin and slightly bubbly, roughly the texture of chocolate milk (yep, really that thin). Carefully pour the batter into the loaf tin, leaving about 1 1/2 inches between the batter and the top of the pan. With any remaining batter fill some muffin cases.
4. Bake the loaf for 30 minutes at 190 C. Then turn the oven down to 165 C and bake for a further 10 minutes (15-20 if using a 9×5 pan). For the muffins, bake at the higher temperature for 12 minutes and then remove from the oven.
5. Remove the loaf from the oven and leave to cool completely in the pan overnight. Serve next day.
Makes 1 8×4 loaf plus 4 muffins, or 1 9×5 loaf. Keeps well at room temperature in an airtight container.