Bring a large pot of lightly salted water to a boil over high heat. Prepare an ice-water bath and set aside. Add sugar snap peas to boiling water and cook for 2 minutes. Transfer to ice-water bath until chilled, about 2 minutes. Drain and set aside. If using fresh peas, add to boiling water and cook until just tender, 4 to 6 minutes; drain and transfer to ice-water bath until chilled, about 2 minutes. Drain and set aside.

Place sugar snap peas and milk in the jar of a blender; blend until pureed. Transfer to a medium bowl and whisk in heavy cream and egg until well combined. Add flour, baking powder, salt, and sugar; mix to combine. Place peas in the bowl of a food processor; process until smooth. Add to medium bowl and stir to combine.

Place 1 tablespoon butter in each of two large ovenproof skillets and melt over high heat. Add 2 tablespoons batter to pan to create a 3-inch-round pancake, making four pancakes per skillet. Cook until edges start to brown, 1 to 2 minutes; transfer to oven and cook 2 minutes more. Turn pancakes and return to oven until lightly browned, about 4 minutes.