We peel and cut the potatoes, to cook them in salted water. We put it all through a food processor.

Add the milk with cream, the Manchego cheese, the butter, and season.
We mix with pisto manchego and add the tuna.

We put layers of: mashed potatoes, Manchego ratatouille with tuna and again mashed potatoes. In the last layer we add grated Manchego cheese.

Gratin in the oven.