Double Chocolate Beet Muffins

1 c. whole wheat flour
1 c. all-purpose flour
2 tsp. baking powder
1 t. baking soda
1/2 tsp. salt
1/2 c. bittersweet chocolate chips
1/4 c. butter
2/3 c. bittersweet chocolate chips
3/4 c. brown sugar
2 eggs, lightly beaten
1 c. beet puree*
2/3 c. buttermilk
1 tsp. vanilla extract
*To make beet puree: Remove greens from beets and boil for 35-40 minutes. When cool, the skins should slip right off. Puree beets, adding a little bit of the cooking water, until they reach the consistency of applesauce.
1. Preheat oven to 375 degrees.
2. Grease a 12-cup muffin tin or line it with paper cups; set aside.
3. In a large bowl, whisk together first 5 ingredients until well combined. Stir in the half cup chocolate chips; set aside.
4. In a small saucepan, melt the other 2/3 cup chocolate chips and butter over very low heat. Stir to combine and set aside to cool until lukewarm.
5. In a medium bowl, whisk together eggs, brown sugar, beet puree, buttermilk, vanilla and melted chocolate.
6. Pour the chocolate mixture into the dry ingredients and stir with a spoon until just combined.
Immediately spoon batter into 12 well-greased or paper-lined muffin cups. Batter should completely fill the cups.
Place muffin pan in the oven and bake for 18-20 minutes.
Cool muffins for 10 minutes in pan then remove them to a wire rack to cool