Buckwheat tortelli with Bitto, potatoes and cabbage in butter and sage

A reworking of Valtellina pizzoccheri, delicious and flavourful. I could not find Bitto and Casera, the traditional cheeses I usually use, so used Branzi and Malga Novezza cheese with excellent results. Choose flavourful cheeses.
This makes many ravioli; I usually allow 5/6 per person, but you will be asked for more. I froze leftovers.
INGREDIENTS FOR 52 TORTELLI
PASTA
200 g buckwheat flour
200 g '00' flour
4 eggs
FILLING
600 g potatoes, weighed after boiling
100 g grated Bitto
100 g grated Casera
Salt, pepper
SAUCE
Butter
Extra virgin olive oil
Sage
GARNISH
Savoy cabbage
Shavings of both cheeses
Extra virgin olive oil
Salt, pepper
I made dough and filling the day before and refrigerated wrapped in cling film.
I mix both flours on the board, make a well, add lightly beaten eggs and start combining.

I knead by hand; a mixer works too.

I work for about ten minutes until smooth, firm and even, wrap and refrigerate. If made the day before, put in a food bag too.

I wash and shred half a small cabbage (for 4 people), stew in oil with water if needed until tender, salt and set aside.

I boil potatoes, weigh 600 g, rice while hot and combine with cheeses chopped in a processor.
I add very little salt and pepper.

I mix well and rest.

Everything is ready; now the tortelli.

I take half the dough from the fridge, keeping the rest wrapped so it does not dry, and cut into pieces.

I lightly flour and flatten a piece, rolling one sheet at a time and keeping others wrapped.

I pass through the widest rollers. Do not worry if crumbly at first: fold in half and pass repeatedly without flour so it grips. Gradually narrow to a thin sheet.

At the desired thickness, I arrange large filling balls, spaced apart.

I dampen edges and gaps between fillings with a brush.

I fold pasta in half, press firmly and expel air to seal.

I cut tortelli with a food ring and press edges well.

I prepare one sheet at a time to prevent drying. Rework trimmings; leftover dough can become tagliatelle.

I arrange on floured trays.

I melt butter with a little oil and sage in a large frying pan, move back and forth to emulsify and add a small ladle ravioli cooking water.

I cook tortelli in gently boiling salted water for about 5 minutes, keeping the boil gentle so they do not break.

I gently lift with a slotted spoon into melted butter, heating a couple of minutes and spooning over butter and sage.

I put reheated cabbage on plates, add tortelli and coarsely grated cheese, then spoon over butter and sage.