So, what do we have here?
A boyfriend's birthday, a huge jar of dulce de leche from Minas (I think it was 500g, maybe more), and some great peanuts.
For me, it seemed like a good idea to turn it all into a cinnamon cake filled with a peanut crispy and dulce de leche. I adapted this recipe for the cake dough, which came out a bit too dry, but even so it tasted nice, and the result was the cake in the pictures.