Preheat the oven to 180 ÂșC. Butter an 20cm springform pan with removable bottom and line the bottom with parchment paper. Set aside.
First make the topping: put all the crumble ingredients in a bowl and rub together until crumbly.
In a medium bowl, whisk together the flour, ground almonds, baking powder, and salt. Set aside
In a large bowl, using an electric handheld mixer, cream together the butter, the sugar, the vanilla, and the almond extract for several minutes until they are fluffy and well mixed.
Add the egg and beat it in. Incorporate the milk.
Add the whisked dry ingredients and stir everything together on low to form a smooth cake batter.
Pour the cake batter into the prepared springform pan. Smooth it out.
Scatter the black currant berries over top, then pieces of the soft crumble topping and the sliced almonds.
Bake the cake on the middle rack of the oven until the edges are golden brown and a cake tester inserted in the middle comes out clean. It took about 60 minutes for this cake to bake properly in my oven.
Let cool slightly before running a knife around the edge of the cake and then unclipping the springform to release the sides. Transfer the cake to a wire rack to cool completely.