- 1 pound bittersweet (not unsweetened) or semisweet chocolate, chopped
- 3/4 cup (1 1/2 sticks) unsalted butter, room temperature
- 2 ounces unsweetened chocolate, chopped
- 2 teaspoons instant espresso powder
- 3 cups sugar
- 1 12-ounce can fat-free evaporated milk
- 1 1/2 cups walnut pieces, toasted
- 1 tablespoon vanilla extract
- Line 13x9x2-inch metal baking pan with foil, leaving overhang.
- Combine first 4 ingredients in large bowl.
- Stir sugar and evaporated milk in heavy large deep saucepan over medium heat until sugar dissolves and mixture comes to boil. Attach clip-on candy thermometer to side of pan. Boil until temperature registers 234°F, stirring constantly and adjusting heat to avoid boiling over, about 10 minutes.
- Immediately pour milk mixture over chocolate mixture. Whisk until chocolate and butter melt and fudge is smooth. Mix in nuts and vanilla.
- Spread fudge evenly in prepared pan. Refrigerate uncovered until cold and set, about 3 hours.
- Using foil as aid, lift fudge from pan. Cut crosswise into 7 strips, then lengthwise into 5 strips. Return to pan, cover, and chill. (Can be made 2 weeks ahead. Keep covered and chilled. Bring to room temperature before serving.)