- Line an 8x8x2-inch baking pan with foil, extending the foil over edges of pan. Butter foil; set pan aside.
- Butter the sides of a 3-quart heavy saucepan. In the saucepan, combine granulated sugar, half-and-half, brown sugar, cocoa powder, coffee crystals, corn syrup, butter, and salt. Cook and stir over medium heat until mixture is boiling. Clip a candy thermometer to the side of the pan. Reduce heat to medium-low; continue boiling at a moderate, steady rate, stirring occasionally, until thermometer registers 236 degrees F, soft-ball stage (about 25 minutes). (Adjust heat as necessary to maintain a steady boil.)
- Remove saucepan from heat. Add vanilla but do not stir. Cool, without stirring, to 110 degrees F (50 to 60 minutes). Remove thermometer from saucepan. Beat mixture vigorously with a clean wooden spoon just until candy starts to thicken. Continue beating just until fudge starts to lose its gloss (6 to 8 minutes total). If desired, quickly fold in 1/2 cup chopped coffee beans.
- Immediately spread fudge evenly in the prepared pan. Score fudge into squares while warm. Let fudge cool to room temperature. When fudge is firm, use the edges of the foil to lift fudge from pan. Cut into squares. If desired, pipe or spoon a little chocolate frosting onto each square and top with a halved coffee bean.
From the Test Kitchen
Layer fudge between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to 1 week.