Prepare the Pan: Line a 9x9-inch square baking dish with parchment paper, leaving some overhang for easy removal later. Lightly spray the paper with cooking spray to prevent sticking.

Make the Marshmallow Mixture: In a medium saucepan, combine the granulated sugar, corn syrup, and water. Cook over medium heat, stirring until the sugar is dissolved. Increase the heat to medium-high and bring the mixture to a boil without stirring. Continue boiling until it reaches 240°F (soft ball stage) on a candy thermometer.

Whip the Egg Whites: While the sugar mixture is boiling, beat the egg whites and cream of tartar with an electric mixer in a separate bowl until stiff peaks form.

Combine the Mixtures: Once the sugar mixture reaches 240°F, gradually pour it into the whipped egg whites while mixing on low speed. Once combined, increase the speed to high and whip for about 5-7 minutes until the mixture is thick and glossy. Add the vanilla extract and continue mixing for another minute.

Layer the Graham Crackers: Pour half of the marshmallow mixture into the prepared baking dish and smooth it into an even layer. Lay the graham crackers flat on top of the marshmallow layer (cutting to fit if needed).

Add the Second Layer: Pour the remaining marshmallow mixture over the graham crackers and smooth it out evenly. Allow the Scotchmallows to set at room temperature for at least 4 hours, or until completely firm.

Prepare the Chocolate Coating: Once set, melt the chocolate chips and coconut oil together in a microwave-safe bowl, stirring every 30 seconds until smooth.

Cut and Dip: Lift the Scotchmallows out of the pan using the parchment overhang. Cut into squares. Dip each square halfway into the melted chocolate, allowing any excess chocolate to drip off.

Set the Chocolate: Place the dipped Scotchmallows on wax paper or a cooling rack until the chocolate is completely set.