Step 1

Line an 8" x 8" square or 9" round pan with parchment, and grease the parchment. If you don't have parchment, use waxed paper or plastic wrap.

Step 2

Combine the chocolate, cream, espresso powder, corn syrup, and vanilla in a microwave-safe bowl.

Step 3

Heat the mixture in the microwave (or in a saucepan set over low heat on the stove) until the cream is hot and the chocolate has softened.

Step 4

Remove from the heat, and stir until the chocolate has melted and everything is smooth.

Step 5

Spread about 3/4 cup of the melted chocolate in the bottom of the pan.

Step 6

Space the marshmallow halves atop the chocolate. Note: feel free to substitute mini marshmallows for the marshmallow halves here. Distribute the walnuts evenly in the spaces between the marshmallows.

Step 7

Spread the remaining chocolate atop the marshmallows and walnuts, spreading to the edge of the pan so that everything is covered.

Step 8

Refrigerate for an hour or so, to set the chocolate. Remove from the refrigerator, and loosen the candy from the edges of the pan.

Step 9

Bring to room temperature, and leave in the pan, covered with plastic, until you're ready to cut into squares.