Preheat the oven to 200℃ (180℃ fan)/400°F/gas mark 6. Prick the potatoes all over with a fork and rub with a little oil if desired Bake in the centre of the oven for about 1 hour 15 minutes or until soft when pierced with a skewer.
Meanwhile, wash the leeks and shake dry. Melt the butter in a frying pan and sauté until soft about 5 minutes. Remove from the heat.
Cut the potatoes in half and scoop out the flesh out into a mixing bowl leaving the skins intact. Place the hollowed out skins on a baking sheet.
Cut the brie into pieces and mix into the potato flesh, mashing the flesh as you do so. I found this easiest to do with a dinner knife
Add the leeks, season with salt and pepper and mix well. Pile back into the potato skins.
Return to the oven for 15 minutes to heat through then serve immediately.
Nutrition information is approximate and is meant as a guideline only. (It does not include seasoning with salt and pepper.)