Expresso Shortbread Cookies

In a large bowl, use a mixer to beat together butter and sugar until light and fluffy. Add vanilla, salt, espresso grounds, and coffee liqueur. Beat to combine. Add flour and mix until it’s well blended. Then form the dough into two 1½" thick logs, cover with plastic wrap or wax paper, and chill at least 2 hours or overnight. Preheat oven to 325° F. Cut chilled dough into ¼" 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. Melt chocolate, add espresso powder and drizzle over cooled cookies.