Measure out 300g of the potato purée, straight from the freezer, and leave to defrost in a bowl. Meanwhile, grate the provolone cheese.
In a saucepan, cook the spinach in water over a high heat. Once ready, drain the spinach, leave to cool and then squeeze it and chop it coarsely.
Combine the spinach with the potato purée, the grated Parmesan, the provolone, one egg white, the nutmeg and four tablespoons of breadcrumbs. Add salt to taste. The mixture should be quite compact.
Roughly chop the pine nuts and combine them with 100g of Panko bread.
Shape the croquettes and then roll them in the rice flour, the remaining egg white and the Panko bread. Cook the croquettes in a non-stick pan with a drizzle of oil until golden.
Serve the croquettes with a fresh salad.