Cream together the brown sugar and room temperature butter.
Whisk together the wet ingredients, melt the chocolate and add the dry ingredients to the creamed butter/sugar. They do not need to be added separately or in any particular order.
The dough will be very sticky. You'll need to cover the dough and refrigerate for at least an hour or so.
Preheat oven to 350 degrees and line baking sheets with parchment or silicone mats.
Using a cookie scoop, place mounds directly into sugar and roll. Place on a lined cookie sheet and using a small glass or measuring cup, lightly press to flatten. Dipping the glass in the sugar will keep it from sticking. Coat the flattened rounds in sugar once again.
Place a walnut half on each round and lightly press.
Bake for about 12 minutes and allow to cool for 5 minutes on the baking sheet until they are firm enough to remove to a rack to cool completely.