Though I've suggested using tempered chocolate to dip these, this recipe is particularly forgiving of untempered chocolate. Just dip them within 24 hours of when you want to serve them if you don't want unsightly bloom. You can, of course, reduce the amount of espresso powder if you're a wuss.
2 Tbsp. instant espresso powder
1 Tbsp. vanilla extract
1 cup salted butter, thoroughly softened
3/4 cup sugar
2 1/2 cups all-purpose flour
12 oz. bittersweet chocolate
Combine the espresso powder and vanilla extract in a small cup and stir until dissolved. In a large bowl, cream the butter, then add the sugar and mix thoroughly. Add the espresso syrup and beat until uniform. Add the flour and stir gently, just until thoroughly combined.
Position a rack in the upper third of the oven and preheat to 300°F.
Shape little pieces of dough (about half a tablespoon) into logs about 1 1/2 inches long by 1/2 inch thick. You should get about 50. Place them on ungreased cookie sheets, leaving room for expansion, and flatten them to 1/4 inch thick. Bake for 35-45 minutes, or until they are browned on the bottom (which is difficult to tell, since they're pretty brown anyway) and feel fairly firm when gently poked. Remove them from the cookie sheets to wire racks and cool completely.
Temper the bittersweet chocolate. Dip the cookies, covering most of their length, shake gently to remove excess chocolate, and place them on paper to set. Store them in airtight containers; the texture will be best the next day.