Pre-heat the oven to 425 degrees F and bring a large pot of water to a boil. Place cranberries in bowl of hot water to soak. Toss the green onions with 1 tablespoon of olive oil and season with salt and pepper. Place on a sheet tray and roast in the oven until lightly charred, about 10 minutes. Remove the onions from the oven and let them cool down. In a blender combine the onions, cashews and Parmigiano cheese, pulse for 5 seconds. Slowly drizzle in the remaining olive oil and season with salt and pepper to taste. Add the ice cubes and puree. Remove the pesto from the blender and place in a large bowl. Cook the pasta according to the package directions, drain reserving 1/2 cup cooking liquid. Drain cranberries. Add the cooking liquid, pasta and drained cranberries to the pesto, then stir to combine.