Melt ½ cup butter in a small saucepan on stove or microwave. Add cocoa powder and espresso powder to form a paste. Set aside.
Beat remaining butter and sugar for one minute until light and fluffy. Beat in cooled cocoa mixture until combined.
Add egg and vanilla and beat for another 30 seconds.
Add flour in 3 equal parts, incorporating each before adding the next. Roll the dough into a 2 inch diameter cylinder, wrap in parchment paper and chill for at least one hour.
When ready to bake, preheat oven to 375 degrees.
Slice cookie dough in ¼ inch thick slices. Place circles on cookie sheet about an inch apart.
Bake until cookies are set about 10-12 minutes. Let sit on baking sheet for 3 minutes then move to a cooling rack to cool completely.
Melt chocolate and coconut oil and drizzle over the cookies. Let harden before serving.
Notes
For chocolate flavor only add 1 teaspoon of espresso powder
For a Mexican version add 1 teaspoon cinnamon and ⅛ teaspoon cayenne pepper
roll dough and cut like sugar cookies instead of cutting into disks