Make the filling: in a mixing bowl, gently stir together 250g of ricotta, 250g of mascarpone, the grated zest of 1 small orange, 2 tbsp of icing sugar and 1 tbsp of finely chopped pistachios.
Melt 30g of unsalted butter in a pan, remove from the heat and allow to cool. Put 100g of plain flour into a blender. Mix together 1 large egg and an egg yolk, pour in 350ml of milk and add to the flour. Add the butter and process briefly to a thin batter. If there’s time, let the batter rest for half an hour. Finely grate the zest from 1 small lemon, then stir into the batter.
Melt 50g of butter in a small pan, then remove from the heat. Warm a nonstick shallow pan over a moderate-to-low heat, then pour in 1 tbsp of the melted butter. Pour a ladleful of the batter into the pan and twist left and right and back and forth until the base is covered with a thin layer.
Cook the pancake over the heat until it is golden on the underside then, with the help of a palette knife, flip it over and cook the other side. Slide out on to a warm plate. Add a little more butter to the pan, then repeat until you have 6 thin pancakes.
When the pancakes are cool, divide the filling between them, spreading it thickly over the surface. Loosely roll each pancake up and place them in a shallow, heatproof baking dish. Dust generously with icing sugar. Warm an overhead grill.
Remove the peel from 2 medium-sized blood oranges, then slice into segments. Roughly chop 2 tbsp of shelled pistachios. Place the rolled pancakes under the hot grill for a few minutes until the sugar has started to caramelise. Scatter the oranges and chopped pistachios over the warm pancakes and serve. Enough for 4