i used my cobnuts to make an apple and cinnamon cake. the recipe i used was a nigel slater one for moist plum cake (see here for a cherry & almond version, including the recipe which you can adapt if you fancy giving this a try) which uses a mix of flour and ground almonds.
i blitzed the cobnuts in my food processor and used this in the place of the almonds. a teaspoon of cinnamon into the mix and pieces of apples on top of the cake mix and that’s it. the cobnuts added an extra depth of flavour, similar to hazelnut. because i used the nuts fresh they were quite coarse which added a really nice crunch to the cake texture.