Heat oven to 190C/170C fan/gas 5.
Peel the potatoes and pat dry with
kitchen paper. Heat the oil and butter
in a flameproof dish, add the potatoes
and brown all over – this will take about
5 mins. Season well, add the thyme
sprigs and stock, and bring to the boil.
Transfer the dish to the oven,
uncovered, and cook for 25-30 mins
until the potatoes are tender.