Preheat oven 350°F. Butter 8 (6-ounce) ramekins or a 1.5-quart soufflé dish. Separate egg yolks from egg whites and allow both to come to room temperature.

In a sauté pan over medium heat, fry pancetta until crisp. Drain on a paper towel, chop finely and set aside. In a large bowl, whisk together pesto and egg yolks. In a small saucepan, heat milk to a simmer and whisk in cheese until melted. Whisk in flour and pepper. Mixture will thicken immediately. Pour contents of pan into pesto-egg mixture and whisk until combined. Allow to cool.

Meanwhile, in a medium bowl, beat egg whites with an electric mixer until stiff peaks form. Gently fold egg whites and pancetta into pesto mixture. Do not overwork, or you will deflate the egg whites. Spoon soufflé batter into ramekins or soufflé dish and transfer to a baking sheet. Bake until puffed and golden, 18 to 20 minutes for the ramekins, 30 minutes for the soufflé dish. A thin knife inserted in center should come out just slightly moist. Serve immediately, as soufflés deflate quickly.