Step 1

Place chocolate in 4-cup glass measuring cup. Place in microwave oven and cook on medium or 50 percent power until chocolate melts and is smooth, stirring every 30 seconds, about 3 minutes total.

Step 2

Line small strainer with double thickness of damp cheesecloth; place strainer over measuring cup with melted chocolate. Pour cream into 2-cup glass measuring cup. Place in microwave oven and bring to boil on high. Stir ground espresso beans into hot cream; let steep 5 minutes. Pour cream mixture into prepared strainer set over chocolate; discard solids in strainer. Stir until cream-chocolate mixture is well blended and smooth.

Step 3

Place butter on plate. Microwave 10 seconds on high to soften. Add butter, 1 piece at a time, to chocolate mixture, stirring until melted. Cover ganache with plastic wrap and chill until firm, about 2 hours.

Step 4

Line baking sheet with waxed paper. Place cocoa powder in medium bowl. Using 1 rounded teaspoon for each truffle, quickly roll chocolate ganache between palms into balls (chill remaining chocolate mixture briefly if mixture softens). Drop each truffle into cocoa powder to coat; shake off excess. Place on prepared baking sheet. Chill truffles until firm, at least 2 hours. DO AHEAD Can be made 2 weeks ahead. Store in airtight container in refrigerator. Dust truffles with cocoa powder before serving.