Preheat the oven to 180°C/gas mark 4. Prepare the batter according to instructions on the packet and make 6 x 20cm pancakes. Set aside.
Heat the olive oil in a frying pan. Add the leeks and sauté until soft. Transfer to a bowl and mix in the peas, torn ham and soft cheese. Season.
Divide the filling between each pancake and roll up. Arrange in an ovenproof dish, sprinkle with the cheddar and bake for 20-25 minutes.