Cook 8 ounces chopped pancetta in a large pot over medium-high heat with 1 tablespoon olive oil until crisp, 6 to 8 minutes. Transfer to a bowl. Add 1 sliced onion and 3 sliced garlic cloves to the pot and cook, stirring, until browned, 8 to 10 minutes; add to the pancetta. Increase the heat to high; add 3 heads chopped escarole, press down and cook, undisturbed, 4 minutes. Toss, season with salt and pepper and continue to cook, stirring, until wilted, 5 minutes. Reduce the heat to medium high; stir in 3/4 cup white wine, then the pancetta mixture. Cook until reduced by half, 4 minutes, then cover and cook until the escarole is tender, 6 minutes. Season with salt and pepper.