Preheat oven to 350 degrees. Line an 8 inch square metal pan with nonstick foil.

Puree the beets (add a little water if they are dry) and measure out ½ cup of puree. Set aside.

In a small to medium size saucepan, melt butter over medium-low heat. Add both sugars and stir until mixture is shiny, then stir in the cocoa powder. Remove from heat and stir in the ½ cup beet puree. Let cool slightly, then add the vanilla.

In a small bowl using a hand-held electric mixer, beat the eggs until they are light and fluffy. With a rubber scraper, gradually stir the beaten eggs into the saucepan with the chocolate mixture.

Mix together the flour, baking powder and salt, and stir flour mixture into the chocolate mixture. Check to make sure the chocolate mixture is not so warm that it will melt the chocolate chips, then stir in the chocolate chips. Scrape mixture into prepared pan and bake on center rack for 27 minutes or until a skewer inserted comes out with moist crumbs.

Let cool for about an hour at room temperature, then transfer to the refrigerator to finish cooling. Lift from pan and cut into squares. Garnish with powdered sugar if desired.