Heat oven to 200C/180C fan/gas 6. Butter 6 dariole moulds or basins well and place on a baking tray.
Put the rest of the butter and chocolate in a heatproof bowl and set over a pan of hot water (or alternatively put in the microwave and melt in 30 second bursts on a low setting) and stir until smooth, then set aside to cool slightly for 15 min.
Using an electric hand whisk, mix in the sugar, then the eggs, one at a time, followed by the vanilla extract and finally the flour. Divide the mixture among the darioles or basins.
You can now either put the mixture in the fridge, or freezer until you're ready to bake them. Can be cooked straight from frozen for 16 mins, or bake now for 10-12 mins until the tops are firm to the touch but the middles still feel squidgy. Carefully run a knife around the edge of each pudding, then turn out onto serving plates and serve with single cream.