2Heat oil in a small skillet over medium. Cook pancetta, stirring often, until brown and crisp, 5–8 minutes. Let cool. Transfer pancetta and fat in skillet to a food processor, add garlic, and process to a smooth paste. Add sage, parsley, chives, rosemary, and lemon zest and process until smooth; set paste aside.
3Pat turkey breast dry and place skin side down on a large rimmed baking sheet so thickest part of breast is closest to you. Run your fingers underneath fillets lengthwise to detach. Using a thin, sharp blade, position knife about 3" from neck end and cut downward at a 45ºF angle into the thickest part of the breast (do not cut all the way through; you're butterflying only the top portion). Open top flap you've just created like a book. Fold fillets in half and place in the top and bottom gaps between the breasts so tapered ends are facing in. The idea is to create a layer of meat of uniform thickness across the entire breast.