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.
In a large skillet, over medium heat, cook the pancetta 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.
Cook until reduced by one-third, about 6 minutes.
If using frozen peas, add them here.
Otherwise, drain the peas, shaking off the excess water, then add to the skillet.
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.
