Preheat oven to 350F. Line a 12 cup muffin pan with silicone or paper cupcake liners.
Cook the quinoa for the cupcakes. In a small saucepan, bring the water and quinoa to a boil. Reduce to a simmer, cover and cook for 15 minutes. Remove from the heat and let sit with the cover on while you do the next steps. Make sure the quinoa is very fluffy with no excess water in it.
Using a hand blender, combine sour cream, honey, egg, egg white, oil and vanilla. Blend until combined. Add ¼ cup of the quinoa and blend until mostly smooth. Repeat adding ¼ cup quinoa, pureeing after each addition, until all the quinoa has been added. Blend about 30 seconds each time. It's ok if it's not completely smooth.
In a medium bowl, whisk together the cocoa, baking powder, baking soda and salt until no lumps of cocoa powder remain. Add the pureed mixture. Stir just until blended. Divide the batter evenly among the cupcake liners.
Bake for approximately 19 minutes or until a toothpick inserted in the center of a cupcake comes out clean. Cool in the pan.
For the icing, peel the avocado and in a small bowl, mash it with a fork until no big lumps remain. Then add the honey and vanilla and whisk by hand until smooth. Add the cocoa powder and whisk again till smooth.