Caramelize the separate granulated sugar with water in a small saucepan until amber, then stir in half the pecans and spread quickly onto parchment to cool.
Cream softened butter with brown sugar, beat in eggs one at a time, and add vanilla; line a round tin and preheat the oven to 175°C.
Whisk flour, baking powder, and salt together, then fold into the butter mixture alternately with milk; incorporate the remaining roughly chopped pecans at the end.
Transfer batter to the prepared tin and bake for thirty five minutes until golden and cooked through, then cool on a rack before adding crunchy decoration.
Break the cooled pecan praline into small shards, reserving the prettiest pieces; melt dark chocolate gently and drizzle thin lines across the surface of the cake.
Press the brittle pieces into the still soft chocolate, allow everything to set, and cut slices with a serrated knife to protect the crunchy topping.
