Put the walnuts in the oven a little, peel them and grind 1/2 of them and chop the rest finely. Mix the flour together with the baking powder and sifted cocoa. Raisins are essentially hydrated and then drained and rolled in flour. The oil is mixed with sugar, raisin essences and vanilla sugar. Add a little lemon juice and the two cups of mineral water, the latter will help a fluffy cake to come out. Gradually add two tablespoons of the mixture of dry ingredients to the liquid and mix at low speed. We also put half of the ground and chopped walnuts until incorporated. Wallpaper a cake form, put some of the dough, raisins, walnuts and keep a little dough. Melt the chocolate in the microwave for 1 minute and place it in the middle of the cake, covering it with the rest of the dough. Put in the preheated oven for 50-60 minutes and then do the toothpick test.
Even if it is made on the edge, check in the middle so that it does not remain raw due to the chocolate. We can add shit or other spices such as cardamom, cinnamon or anise that go very well with chocolate. We can also incorporate melted chocolate in the dough or put finely chopped chocolate. Instead of water, you can use fruit juice, compote juice or soy milk.
The check can be made simple, without chocolate, nuts and raisins in this case it comes out even fluffier.