Preheat the oven to 350 F and line an 8x8inch baking dish with aluminum foil.
Add the graham crackers and granulated sugar to the bowl of a food processor and pulse until finely ground. Stream in the melted butter while the food processor is running until the mixture is moist and crumbly.
Press the graham cracker mixture into the bottom of the prepared baking pan. Transfer to the oven and bake for 10 minutes. Remove from the oven and set aside while you prepare the chocolate.
In a medium saucepan add the condensed milk, chocolate and salt. Cook over medium-low heat stirring constantly until the chocolate is melted and everything is fully combined (take care to not let the chocolate burn).
Spread the chocolate mixture over the graham cracker crust. Chill in the refrigerator for at least 30 minutes.
To make the homemade marshmallow cream topping place the sugar, honey and water in a medium saucepan and stir to combine. Attach the candy thermometer to the side of the pan ensuring the temperature sensor is covered by the liquid.
Cook the the syrup over medium high heat. Once the syrup has reached a temperature of 220 degrees F add the egg whites and cream of tartar to the bowl of your stand mixer (or a large bowl if using a hand mixer) fitted with the whisk attachment. Over medium low speed whip the egg whites to soft peaks, approximately 4 minutes.
Once the syrup has reached a temperature of 240 degrees F remove the pan from the heat. Increase the mixer speed to medium and add in the syrup near the side of the bowl in a slow,steady stream.
Increase the speed to medium high and beat the egg white mixture for 7 minutes or until fluffy and over doubled in size. Add in the vanilla and salt and beat for an additional minute.
Spread the marshmallow cream over the chocolate layer. To toast the marshmallow cream you can use a kitchen torch or your broiler on low for 20-30 seconds until the topping is lightly golden.
Chill the bars for at least 1 hour or up to overnight. Remove the bars from the pan by lifting up the aluminum foil and transfer to a cutting board. To cut clean slices dip your knife into warm water, cut the bars and then wipe off the excess. Repeat the process until all the bars are cut. Serve as desired.