To make the frosting, put the cashews and water into a bowl. Refrigerate for 1 to 2 hours. Drain the cashews and rinse in cold water.

Heat 1 cup nondairy milk in a small saucepan over medium-low heat until simmering. Put the soaked cashews, 1 tablespoon oil, and 3 tablespoons sugar into a blender, then add the chocolate chips.    Pour in the simmering nondairy milk and process for about 20 seconds. Add 1⁄3 cup cold nondairy milk and process until completely smooth. Refrigerate the frosting for 3 hours to firm up.

To make the cupcakes, preheat the oven to 350 degrees F. Line a twelve-cup standard muffin tin and a six-cup standard muffin tin with paper liners.

Put the flaxseeds into a high-performance blending appliance and process into fine flour. Transfer the flaxseed flour to a large bowl. Put the rolled oats into the blender and process into fine flour. Add the oat flour, 11⁄3 cups sugar, almond flour, cocoa powder, baking powder, baking soda, and salt to the flaxseed flour, and stir with a dry whisk to combine.

Make a well in the center of the dry ingredients. Add 11⁄3 cups nondairy milk, 1⁄3 cup oil, and vanilla and stir to incorporate. (If batter seems loose, add 1 more tablespoon almond flour.)

Divide the batter evenly among the 18 muffin cups. Bake for 32 to 37 minutes, or until a toothpick inserted in the center of a cupcake comes out clean.

Transfer the cupcakes to a wire rack and let cool completely. Pipe or spoon a generous amount of frosting over the top of each cupcake. Covered tightly and stored in the refrigerator, leftover cupcakes will keep for about 3 days.