Place the sugar and eggs in a large bowl and beat together until the mixture is light and fluffy.
Make the coffee. While it brews, sieve the flours and yeast together. This will result in an even lighter and fluffier dough. Add the flours to the egg mixture, alternating them with the freshly made coffee and the peanut oil and mixing it all together with an electric whisk at low speed. When the mixture is soft and smooth, pour it into a well-greased ring cake mould. Before baking, remember to sprinkle coarse-ground salt over the surface. Bake at 170°C (338°F) for 40 minutes.
Make the coffee. While waiting for it to cool down, chop the gianduja chocolate into pieces.
Place the egg yolks and sugar in a bowl, and whisk them together until smooth. Meanwhile, heat the double cream in a small pan. Once it has reached boiling point, add the yolk and sugar mixture. Note that once the eggs have been added, it is important to keep mixing it with a whisk over a low heat without bringing it back to the boil. Otherwise, you may end up with something resembling an omelette! The cream is ready when a thin layer sticks to the spoon. Remove from the heat and add the gianduja to the mixture, stirring it in until it has fully dissolved. Now pour the ganache over the ring cake until it covers it completely.