Preheat the oven to 200C/gas 6/fan 180C. Put the lactose free cream in a pan and whisk over a medium heat until the mixture boils and thickens.
Reduce the heat and simmer for 5 minutes. Remove from the heat, stir in the Parmesan and half the gruyère and season with salt and ground black pepper.
Pour one third of the sauce into a bowl and stir in the low FODMAP pesto. Lay out the pancakes and spoon a dollop of sauce in the centre of each one. Top with the chicken and then fold in the sides of the pancakes and roll them up.
Arrange the pancakes in a single layer in a buttered large shallow baking dish (about 25 x 30cm) and pour over the remaining sauce.
Scatter with the rest of the gruyère. (If making ahead, cool, cover and chill for up to a day, or freeze for up to a month.) Bake, uncovered, for 30 minutes until the sauce is bubbling and golden. Serve with a green salad.