Ingredients

Base:
1 kg red potatoes (potatoes for making gnocchi)
1 egg
1 kg flour
Salt

Filling:
500 gr spinach
Butter
Parmesan cheese

Boil the potatoes (pressure cooker about 15 to 20 min. From when it whistles). 
Once cooked let them cool. 

On a pastry board spread the flour. 
Peel the potatoes and squeeze them with a potato squeezer, they should be cold and absolutely no longer hot, arrange them in a fountain on the pastry board and in the middle break an egg, add salt to taste. 
Start kneading by adding flour until the dough no longer sticks to your hands (there may be leftover flour).
Roll out the dough/sheet so that it is one finger thick on a suitably floured tea towel. 
Add spinach already stewed in butter and cooled. 
Roll up the pastry sheet like a strudel, wrap it in the dishcloth, tie the ends of the dishcloth with twine and cook in boiling water for about an hour.

At this point untie the dishcloth, cut into slices and serve accompanied by a roast gravy.

If you do not have a roast gravy you can make a quick sauce: in a small pan melt some butter, add breadcrumbs, brown it being careful not to burn it, it only takes a moment.
Remove it from the heat and accompany the slices of spinach roll. At the end add plenty of Grana cheese.