Preparation

Melt the butter and let cool to room temperature. Add the egg yolks and whip by hand. Add the milk and salt. Add the grated Parmigiano and, with a sieve, the flour and yeast. Blend everything with a whisk until smooth and even in consistency. In a separate bowl, use an electric whisk to beat the egg whites to stiff peaks. Combine with the other mixture. When uniform and fully blended, pour 1 ladle-full into a non-stick saucepan coated with butter. Make pancakes that are about 10 cm in diameter. Cook on one side until golden brown, flip and cook on the other, approx. 1 minute per side. As you gradually remove the pancakes from the saucepan, stack them on a plate. While they're still warm, place alternating layers of 1 slice of cheese and 1 slice of prosciutto between them.