Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease ramekins (each with a capacity of approx. 150 ml) and sprinkle with sugar. Chop chocolate, melt with 100 g butter at low heat.
Leave to cool for about 5 minutes. Whisk eggs, egg yolk and 60 g sugar with the whisk of the mixer for about 5 minutes until creamy. First stir in flour, then chocolate butter.
Fill half the dough into the moulds. Add 1 tsp. peanut butter to each pan. Cover with the rest of the dough. Bake in a hot oven for about 12 minutes.
Remove the cakes and let them cool down for about 3 minutes. Loosen the inside edge of the mould with a knife. Turn out onto plates and serve immediately.