Caramelized apple and walnut cake: Stage 1

The walnuts

Take 100 g butter out of the fridge and leave to soften at room temperature.

Preheat the oven to 300°F (150°C).

Spread out 100 g walnut kernels on a sheet of cooking parchment laid on a baking sheet, and toast the walnuts in the oven for 15 minutes.

Leave to cool.