Preheat oven to 325°. In a large bowl, use a mixer to beat together butter and sugar until light and fluffy. Add vanilla, salt, espresso grounds, and Kahlúa. Beat to combine. Add flour and cacao nibs and mix until well blended.
Form dough into two 1 1/2-inch-thick logs, cover with plastic wrap or wax paper, and chill at least 2 hours or overnight.
Cut chilled dough into 1/4-inch-thick slices and lay slightly apart on ungreased cookie sheets. Bake until cookies are browned on the bottom but not the top, 15 to 20 minutes. Transfer to a rack to cool.
Note: Nutritional analysis is per cookie.