For the muffins:
1¾ cups all-purpose flour
½ cup sugar
1½ tsp. baking powder
½ tsp. baking soda
¼ tsp. coarse salt
Grated zest of 3 blood oranges
4-6 oz. bittersweet chocolate, coarsely chopped
8 tbsp. unsalted butter, melted
2/3 cup freshly squeezed blood orange juice
1 tsp. vanilla extract
2 large eggs
For the glaze:
¼ cup sugar
¼ cup blood orange juice
Preheat the oven to 400˚ F. Line muffin tins with paper liners. In a large bowl, combine the flour, sugar, baking powder, baking soda, salt, and orange zest. Whisk to blend. Stir the chocolate chunks into the dry ingredients. In a medium bowl combine the melted butter, orange juice, vanilla and eggs. Whisk to blend. Add the wet ingredients to the bowl with the dry ingredients and fold together gently just until combined. Divide the batter between the prepared muffin cups, filling about ¾ full.
Bake 18-20 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool in the pan briefly, then transfer to a wire rack.
While the muffins are baking, making the glaze. Combine the sugar and blood orange juice in a small saucepan over medium-high heat. Cook, stirring occasionally, until the sugar has dissolved. Remove from the heat. Brush warm glaze over the muffins as they cool.