For the stuffed mushroom garnish, sauté the onion in oil until translucent, add the ground meat, season with salt and pepper, and fry for about 8-10 minutes, until cooked through.
Remove from the heat, mix in the breadcrumbs and the egg, so the filling holds together.
Stuff the mushroom caps with the meat filling, place on a buttered baking sheet, and bake at 180°C for 15-18 minutes (sprinkle with grated cheese in the last few minutes, if using).
Meanwhile, beat the eggs thoroughly with the cream and a pinch of salt.
Heat the butter or lard in a pan, pour in the egg mixture, and cook over medium heat, occasionally shaking the pan, so it cooks evenly.
When only the top is slightly wet, roll up the pancake.
Place on a plate, arrange the baked, stuffed mushroom caps alongside, and serve immediately.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.