Bring a large pot of salted water to a boil. Add the green beans and cook until just tender, but still crisp, about 2 minutes.

Drain and immediately plunge into a bowl of ice water to stop the cooking. Drain again and place on a clean kitchen towel to dry.

Add the olive oil and pancetta to a cold, large skillet then turn the heat to medium.

Cook, stirring occasionally, until it renders its fat and turns golden brown, about 5 minutes.

Remove the pancetta with a slotted spoon, leaving the fat in the pan, and drain on paper towels. Reserve for garnish.

Add the shallots to the pan and cook until softened and just starting to turn golden, about 4-5 minutes.

Pour in the chicken stock, then let it simmer until it reduces by half, about 3-4 minutes.

Add the blanched green beans and toss to coat. Season lightly with salt and pepper to taste.

Add the vinegar and butter, and then toss the beans around until they’re warmed through, the liquid has reduced and the butter emulsifies into a glossy sauce, about 2-3 minutes.

Taste and adjust seasoning, then transfer to a serving platter.

Sprinkle the reserved pancetta over top, then serve immediately.