Step #1 Position racks in the lower & upper third of the oven & preheat to 325F degrees F.
Step #2 Line 3 baking sheets with parchment or silicone mats.
Step #3 (If you don't have 3 pans, simply cool the pan between batches.
Step #4 ).
Step #5 Put the butter & the unsweetened & semisweet chocolates in a medium microwave-safe bowl.
Step #6 Heat at 75 percent power in the microwave until soft, about 2 mins.
Step #7 Stir & heat again until melted, up to 2 mins more.
Step #8 (Alternatively, put the chocolates & butter in a heatproof bowl.
Step #9 Bring a saucepan filled with an inch or so of water to a very slow simmer; set the bowl over, but not touching the water, & stir every once in awhile until melted & smooth.
Step #10 ).
Step #11 Stir the light brown & granulated sugars & vanilla into the chocolate mixture with a wooden spoon.
Step #12 Add the eggs & buttermilk & beat vigorously until thick & glossy.
Step #13 In another bowl, cocoa, whisk the flour, cinnamon & salt together.
Step #14 Add the dry ingredients to the wet & stir until just mixed.
Step #15 Stir in chocolate chunks & dried cherries, if using.
Step #16 Drop the batter in heaping tbsps onto baking sheets--a small ice cream scoop is ideal for this.
Step #17 Space the cookies about 2-inches apart.
Step #18 Bake until the cookies set but are soft & fudgy on the inside, 12 to 15 mins.
Step #19 Cool cookies on the baking sheet for 5 mins, then transfer to a rack to cool completely.
Step #20 Serve.
Step #21 Store cookies in a tightly sealed container at about room temp for up to a week.