Cook the potatoes in boiling salted water for 5 minutes. Meanwhile make 2-3 deep cuts in each chicken drumstick and place in a bowl with the onions. Mix together the remaining ingredients with 150ml (¼pt) water and pour over, coating the meat mixture well.

Drain the potatoes, toss in a little butter then place in the warm gratin dish with the chicken and sauce. Cover with foil and bake for 15 minutes. Uncover and continue to cook for a further 20 minutes until the sauce has reduced and coated the chicken well.