Preheat an oven to 400°F. Oil 12 muffin cups or line with paper liners. Soak the Amaz!ns™ and sour cherries in warm tap water for 5 minutes. Drain. In a bowl, whisk together the flours, cocoa powder, sugar, baking powder, baking soda and salt. In food processor, puree prunes and water. In another bowl, whisk together the buttermilk, sugar, eggs, butter, prune purée and vanilla. Mix the buttermilk mixture into the flour mixture until just combined. Fold in the Amaz!ns™, cherries and chocolate chunks. Fill the prepared muffin cups just below the rim. (Each muffin will have about 85 grams of batter.) Sprinkle coarse sugar on top. Bake until a skewer inserted into the center comes out clean, about 18 minutes. Cool for 5 minutes, then remove from the muffin cups and cool completely.