Preheat the 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 skillet over medium heat, fry pancetta, stirring occasionally, until crisp and browned, about 4 minutes.

Drain on a paper towel 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.

Set aside to cool slightly, then pour pan into pesto-egg mixture and whisk until combined.

Allow to cool completely and stir in pancetta.

Meanwhile, in a medium bowl, beat egg whites with an electric mixer until stiff peaks form.

Gently fold egg whites 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.