Bring a large pot of salted water to a boil over high heat. Fill a large bowl with ice water. If using fresh English peas, add to the boiling water and cook until tender, about 1 minute. Add the snap peas and cook until bright green, about 2 minutes, then add the snow peas and cook 30 seconds. Drain the peas and plunge into the ice water to cool.
Cook the pancetta in a large skillet over medium heat until crisp, 8 to 10 minutes. Transfer to a paper towel-lined plate with a slotted spoon. Add the flour to the drippings in the skillet and cook, whisking, until toasted, about 1 minute. Whisk in the chicken broth and cream and cook until reduced by one-third, about 6 minutes.
Drain the peas, shaking off the excess water, then add to the skillet (if using frozen peas, add them here). Cook, stirring, until heated through, 3 to 5 minutes. Stir in the lemon juice and season with salt and pepper. Transfer to a serving bowl and top with the pancetta.