Cut 1 leek into very thin 2-inch strips; chop remaining leek. In saucepan, heat oil over medium-high. Cook leek strips until golden, 2 minutes. Transfer to paper towels; season. Cook chopped leeks over medium, 3 minutes. Add peas and stock; cook 5 minutes. In blender, puree with mint and lemon juice; season. Top with sour cream and frizzled leeks.
Fry right: To get crispy leeks that aren’t greasy, you need rippling hot oil. Drop a couple of leek strips into your oil, and if they start to sizzle right away, it’s fry time!