Preheat oven to 375°. In a large skillet, heat oil over medium-high heat; saute onion, garlic, ginger, cumin and jalapeno until onion is tender. Stir in seasonings until blended. Add mashed potatoes, peas and lemon juice; cook 4 minutes, stirring occasionally. Cool slightly. Stir in cheese, cashews and cilantro.
Unfold puff pastry. Cut each sheet into six rectangles; moisten edges lightly with water. Spoon about 2 tablespoons potato mixture down the center of each rectangle. Fold a long side over filling, fold short sides toward the center, then roll up. Press seams to seal. Place 2 in. apart on a greased baking sheet, seam side down.
Bake until golden brown, 18-22 minutes. Place remaining ingredients in a blender; cover and process until blended. Serve with pastries.
Every editorial product is independently selected, though we may be compensated or receive an affiliate commission if you buy something through our links.