In the same skillet, melt 2 tbsp of the butter over medium heat. Add shallots and pancetta; sauté until shallots are softened, about 2 minutes. Stir in rice until well coated (do not let brown). Stir in wine and cook, stirring constantly, until liquid is absorbed. Stir in 1/2 cup stock and cook, stirring constantly, until stock is absorbed. Continue adding stock, 1 cup at a time, stirring constantly until absorbed before adding more. It will take about 20 minutes to incorporate all the liquid.