Wash the potatoes and boil in boiling water for 25-30 minutes until soft. In the meantime, clean and wash the rocket and chop it coarsely, except for a few small ones for garnishing. Roast the walnuts in a pan without fat, then chop them finely.
Set aside 1 tablespoon of nuts for garnishing. Mix ricotta, nuts and chopped rocket and season to taste with salt and pepper. Drain the potatoes, rinse briefly in cold water and peel.
Press hot potatoes through a potato ricer. Add egg yolks and starch, mix and season to taste with salt, pepper and nutmeg. Fill potato mixture into a piping bag with star-shaped spout and squirt 4 rings (approx. 8 cm Ø) each onto 2 baking trays lined with baking paper.
Press 1-2 teaspoons of ricotta in the middle of each. Place 1 egg on each. Bake the potato nests in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 20 minutes. Meanwhile bring the stock, milk and cream to the boil and simmer for about 5 minutes.
Cut the cheese into small pieces, stir into the cream and simmer for another 3-5 minutes. Season sauce with salt and pepper. Remove potato nests from the oven, garnish with rocket and chopped walnuts and serve with sauce.