Preheat the oven to 160°C/320°F/gas 2. Break up the chocolate, put it into a food processor with the butter, sugar, almonds, 1 tablespoon of the cocoa powder and the salt, and whiz until smooth. Crack your eggs, one at a time, into the food processor and add the flour. Whiz again until smooth.
Get a deep baking dish roughly 25 x 25cm in size. Butter the dish really well and sprinkle the remaining tablespoon of cocoa powder over it. Shake it around a bit so it lightly coats the whole surface of the dish. Pour the cake mixture into the dish, using a spatula to scrape it all out of the processor. Break the fudge into pieces and sprinkle these over the top of the cake mix, pushing any larger pieces down into the mixture.
Pop the baking dish into the preheated oven and cook for 18 to 20 minutes. Take the cake out of the oven and stick a fork into the middle of it. If there’s a little bit of cake mixture on the fork when you pull it out, that’s okay – you want the cake to still be a little moist inside so that it’s nice and squidgy. However, if it seems a bit wobbly, pop it back into the oven for another 3 to 5 minutes to firm up a bit.
Let your cake cool slightly and serve it warm and gooey. Lovely with a dollop of crème fraîche, a scoop of vanilla ice cream or a bit of double cream.