In a large saucepan, cover the rinsed rice with 2 cups of water. Season with salt and bring to a boil. Cover and cook over low heat for 17 minutes. Uncover and place a clean kitchen towel over the pot. Replace the lid and let stand off the heat for 10 minutes. Fluff the rice and let cool slightly.
Meanwhile, add the kimchi and 1 tablespoon of water to a blender or mini food processor and puree. Heat the oil in a large nonstick skillet. Add the Spam slices and cook over moderate heat, turning once, until browned, about 4 minutes. Transfer to paper towels to drain.
Arrange 1 sheet of nori with the longer side facing you and rub with a little sesame oil. Mound 1/3 cup of the warm sushi rice on the bottom and pat into an 8-by-2-inch rectangle. Spread 1 scant tablespoon of the kimchi puree on the rice. Top with 2 slices of Spam and another 1/3 cup of the rice. Fold up the rice in the nori, pressing it into a rectangle. Repeat with the remaining nori sheets, sesame oil, rice, kimchi puree and Spam; there may be a little rice leftover. Using a sharp, moistened knife, cut each roll into 6 pieces, wiping the knife with a damp towel between slices. Arrange the musubi on a platter, dot with Sriracha, garnish with the sliced scallion and serve. Makes 2 dozen pieces.
Recipe from foodandwine.com