Preheat oven to 375°F (191°C). Line a 9 x 13 inch pan with foil making sure that there is a 1-inch overhang on the longer sides for easy unmoulding. Lightly grease the foil.
Spread graham crackers into the bottom of the pan in a single layer. Break some of the squares in half to fit around the edges.
In a medium heavy-bottomed saucepan, melt butter over medium heat. Remove from heat. Add and stir in the Redpath® Dark Brown Sugar, heavy cream, and salt. Stir until mixture is thoroughly combined. Place saucepan back onto medium heat. Stir and bring mixture to a boil. Boil for 3 minutes without stirring. Pour mixture as evenly as possible over the graham crackers; do not worry if crackers are not completely covered.
Place baking pan into the preheated oven; about 8 minutes. The brown sugar mixture should be bubbling and spread over the tops of the graham crackers.
Take out of the oven and immediately sprinkle the tops of the graham crackers with the chopped chocolate. Wait about a minute before using an offset spatula or a heatproof spatula to evenly spread the melting chocolate over the crackers (see Chef’s Tips).
Set oven to broil. Wearing oven mitts, move the oven rack to the top third of the oven.
Evenly sprinkle the mini marshmallows over the melted chocolate, covering it completely.
Place pan back into the oven to toast marshmallows; approximately 1 to 3 minutes. Watch carefully to ensure marshmallows do not burn. Rotate pan as necessary. Remove from oven.
Let cool in pan; transfer to refrigerator to chill until chocolate is set; about 30 minutes. Remove using the foil overhangs and lay the slab onto a cutting board. Using a chef’s knife, cut into 3 x 5 inch or 3 x 6 inch pieces.
*Ensure that the heavy cream and sugars are homogenous before placing saucepan back onto the heat to reduce the risk of splitting.
*For a more traditional s’mores bar, replace some or all of the semisweet chocolate with milk chocolate. If a less sweet s’mores bar is desired, replace semisweet chocolate with bittersweet chocolate.
*If chocolate is not spreading evenly or did not melt completely, let the chocolate sit a bit longer before spreading as the residual heat will further melt the chocolate.
*If mini marshmallows are not available, large marshmallows can be substituted, but they will need to be sliced in half or into thirds.
*A kitchen torch can also be used to toast the marshmallows instead of using the broiler function of the oven.
*If desired, place the sliced bars back into the hot oven to reheat the chocolate and marshmallows for a traditional s’mores experience with a gooey interior.
*Redpath® Golden Yellow Sugar or Redpath® Demerara Style Sugar can be used in place of the Redpath® Dark Brown Sugar. Note that by doing so, the resulting bars will have less of a caramel undertone when using the Golden Yellow Sugar and have more earthy notes when using the Demerara Style Sugar.