FOR FILLING: In a Dutch oven or large heavy pot with lid, combine beef, pork, onions, carrots, celery, parsley sprigs and bay leaf. Add cold water to cover by 2 inches. Bring to a gentle simmer; cook, covered, until meat is tender, skimming fat occasionally, about 2 hours.

 

Meanwhile, in a wide heavy pot or large high-sided skillet, melt butter over medium heat. Add shallot and cook, stirring occasionally, until softened, about 5 minutes. Stir in cabbage and generous pinch salt; cook for 2 minutes. Add vegetable broth, bring to a simmer and cook, covered, stirring occasionally, until cabbage is very tender, about 20 minutes. Remove from heat and season with salt to taste. Set aside. 

 

FOR CREPES: In a large bowl, whisk together buckwheat flour, all-purpose flour, eggs, milk and salt. Heat a dry 12-inch nonstick skillet over medium heat. Pour in 6 tablespoons batter, immediately tilting and rotating skillet to coat bottom. (If batter sets before skillet is coated, reduce heat slightly for next crêpe.) Return skillet to heat and cook crêpe until set and golden brown underneath, and air bubbles begin to form underneath, about 4 minutes. Loosen edge of crêpe with a heatproof rubber spatula, then flip crêpe over carefully with your fingertips and cook until just set, 1 to 2  minutes more. Transfer crêpe to a plate. Make 7 more crêpes in same manner, stacking them as cooked.

 

Using a slotted spoon, transfer meat to a large bowl, then strain broth into a large bowl; discard solids. Shred meat, then moisten with 1/2 cup broth; stir in chopped parsley. Season meat and broth in bowl with salt to taste. 

 

Put 4 cups broth in a saucepan and bring to a boil; remove from heat and cover to keep warm. Heat oven to broil.

 

Spoon 1/8 of beef and 1/8 of cabbage across center of 1 crêpe, leaving room to fold over bottom and sides. Fold bottom of crêpe over most of filling, then fold over sides and fold top down to form a packet. Place on a cookie sheet, seam-side down. Repeat with remaining crêpes.

 

Top crêpe packets with Montasio, then sprinkle with Parmigiano-Reggiano. Broil until cheeses are melted and golden, 3 to 5 minutes. Meanwhile, reheat broth.

 

Transfer crêpe packets to shallow serving bowls. Ladle broth into bowls. Sprinkle with Parmigiano-Reggiano and serve immediately.