Melt 1 cm slice of butter in a mug in a 800w microwave for 20 seconds.
Add 1 tbsp brown sugar, 1 tbsp caster sugar, 1 egg yolk and 4 tbsp of plain flour and mix.
Add a few M&Ms to the top and microwave for 5 minutes.
Melt 1 cm slice of butter in a mug in a 800w microwave for 20 seconds.
Add 1 tbsp brown sugar, 1 tbsp caster sugar, 1 egg yolk and 4 tbsp of plain flour and mix.
Add a few M&Ms to the top and microwave for 5 minutes.