Prep the S’more: Start by layering 3 sheets of graham crackers on a pan. Add 2 squares of the chocolate bar (about 1/4 of each bar) on top of the crackers, followed by 2-3 marshmallows. Place another 3 sheets of graham crackers on top to create a sandwich. Repeat this process until you use up all your ingredients. Chill this setup in the refrigerator for at least 1 hour to allow it to firm up.
Make the Batter: In a mixing bowl, whisk together 1 large egg, 1 tsp oil, and 3/4 cup milk until well combined. In a separate bowl, mix 1 cup + 2 tbsp all-purpose flour, 3 tbsp sugar, 1/2 tsp baking powder, and 1/8 tsp salt. Gradually combine the wet ingredients with the dry ingredients until you have a smooth batter. Set aside.
Cut and Prep: Once the chilled S’mores are firm, remove them from the fridge. Cut the stacked S’mores into squares, aiming for about 2 inches per piece. Place them back in the refrigerator while you prepare for frying.
Fry: Heat 1 qt of frying oil in a deep pot to 375°F; use your candy thermometer to monitor the temperature closely. Dip each S’more square in the batter, ensuring it is fully coated. Carefully place the coated squares in the hot oil, frying for about 2 minutes or until they are golden brown. Use a slotted spoon to remove them and drain on paper towels to absorb excess oil.
Serve: These treats are best enjoyed immediately. Serve warm for the ultimate experience, where you can appreciate the contrast of the crispy exterior and the melty chocolate and marshmallow filling!