First of all, to prepare the cheese puffs, grate the fontina and grana padano. Put the butter cut into small pieces in a pan, add the water slowly and put everything to heat on a low flame; then add a teaspoon of salt.

In the meantime, sift the flour that we are going to combine when the butter is completely melted. At this point, mix vigorously with a whisk to prevent lumps from forming. When the dough has compacted, continue to mix, over very low heat, with a wooden spoon until we obtain a smooth and homogeneous mixture that easily detaches from the walls.

Then remove the dough from the heat and put it in a planetary mixer and, with the leaf whisk, start working it by adding and incorporating one egg at a time. When the eggs are all well incorporated, add the parmesan and fontina cheese, previously grated.

When the mixture of the cheese puffs is ready, pour it into a pastry bag with a smooth 10 cm diameter nozzle. On a plate, previously lined with parchment paper, we form 30 piles of dough spaced apart.

We cook the cheese puffs in a ventilated oven at 175 degrees for about thirty minutes. When cooked, turn off the oven and, leaving the cream puffs inside, open the oven slightly for another thirty minutes. This is to ensure that the inside of the puffs dry completely.

When the cheese puffs have cooled down, we can take them out of the oven and stuff them.