In a stand mixer, beat butter and sugar until light and fluffy, about 30-45 seconds.
Add eggs, liqueur (or coffee), and vanilla and beat until evenly incorporated. Scrape down sides of bowl.
In a separate bowl, sift together flour, cocoa powder, baking soda and one teaspoon sea salt.
Add flour mixture to wet ingredients and beat for about 10-15 seconds, then add chocolate chips and beat until even incorporated. Dough will be fairly dry and stiff.
Cover with plastic film and refrigerate dough for at least 30 minutes, up to 24 hours.
In a small bowl combine remaining sugar and 1/4 teaspoon sea salt. Roll dough into 1" balls, then roll in sugar/salt mixture.
Place on ungreased cookie sheet, flatten slightly and bake for 10 minutes at 350 degrees.
After removing from oven, flatten cookie's "dome", and allow to cool on sheet for 2 minutes before transferring to a flat surface to cool.