Beat the eggs, sift in the flour and mix until smooth. Add the mineral water gradually until well combined. Season with salt and pepper.
Clean the button mushrooms and halve or quarter depending on size. Wash and slice the spring onions.
Heat 1 tsp oil in a pan and fry the onions and mushrooms over a medium heat for 5 minutes.
Add the ricotta to the pan, mix well and season with salt and pepper. Remove from the heat.
Stir the pancake batter again. Heat some oil in a pan and add a ladleful of batter.
Tilt the pan to coat the base with batter, then sprinkle with some sesame seeds. Fry the pancake for about 1 minute, then turn and fry for 1-2 minutes on the other side. Continue until all the batter is used and you have 8 pancakes.
Spread the pancakes with the ricotta-mushroom mixture, roll up and place, side by side, in a baking dish.
Mix the sour cream, milk and remaining sesame seeds, season with salt and pepper and pour over the pancake rolls. Bake in a preheated oven at 220°C (200°C fan, gas 7) for 10 minutes.