Place chilled ground veal and egg whites into a food processor, pulse until smooth. Add salt, white pepper, and nutmeg, pulse until fully incorporated.
Add heavy cream and yogurt slowly, pulsing until incorporated.
Add fresh ground bread crumbs and minced sage leaves.
Remove from food processor and shape into 2 ½ oz. portion patties.
Roll patties in lightly in bread crumbs and cover top with prosciutto.
Heat clarified butter in a nonstick skillet large enough to hold patties in one layer without crowding.
Place patties, prosciutto side down, for about 3 to 4 minutes, and turn. Continue cooking for another 2 to 3 minutes, or until golden brown.
Place sage leaf on top of prosciutto and cover with fontina cheese.
Finish in oven until cheese is melted.
Split buns in half and place a slice of tomato on bottom of each bun.
Place a veal patty on top of each tomato slice
Place some frisée on top of patty, drizzle with balsamic vinegar and cover with top of bun.
Nutrition information per serving: 350 k/Cal; 14 (g) Protein; 31 (g) Carb; 2 (g) Fiber; 19 (g) Fat; 7 (g) Sat Fat; 46 (mg) Chol; 724 (mg) Sodium;