Step 1

1 Line an 8-inch-square baking pan with parchment paper, allowing the parchment to overhang on 2 opposing sides

Step 2

2 Lightly coat with nonstick cooking oil spray

Step 3

3 Combine 2 1/2 cups of the chocolate morsels and the coffee or espresso granules in a large bowl

Step 4

4 Drizzle the boiling water over the top; let stand, without stirring, a few minutes so the morsels can soften

Step 5

5 Then slowly stir until the chocolate completely melts and the mixture is well blended

Step 6

6 (If necessary, microwave the mixture in 15-second intervals so that the chocolate melts completely

Step 7

7 ) Add the butter, stirring until melted

Step 8

8 Reserve 3/4 cup of the chocolate mixture for the glaze

Step 9

9 Add the graham cracker pieces, nuts and marshmallows to the large bowl of chocolate

Step 10

10 Chop the remaining 1/2 cup of chocolate morsels into 1/8-inch bits (larger pieces are too hard to eat when chilled) and stir them into the mixture

Step 11

11 Turn out the mixture in the pan, spreading it out and pressing down very firmly using a spatula

Step 12

12 Pour the reserved chocolate glaze over the surface, spreading it evenly

Step 13

13 Rap and shake the pan to even the glaze further

Step 14

14 Let stand until cooled, then cover and refrigerate for at least 1 1/2 hours, until well chilled and firm

Step 15

15 Using the extended parchment as handles, transfer the large square of s'mores to a cutting board

Step 16

16 Discard the parchment

Step 17

17 Using a large knife dipped in hot water and wiped clean between cuts, cut the square into 16 bars

Step 18

18 Let them warm up for a few minutes before serving; they become overly soft if left standing for long periods