Line the bottom and sides of an 8" square pan with a parchment sling that covers the bottom and all sides of the pan. Lightly grease the parchment.

Place the graham crackers in a single layer in the bottom of the pan so that it’s completely covered, breaking the crackers as needed. You’ll use five to six graham crackers.

In a glass measuring cup or small microwave-safe bowl, place the chocolate chips. Heat in the microwave in 30-second increments, stirring between each, until the chips are fully melted. Pour the melted chocolate over the graham crackers, then use a small offset spatula or the back of a spoon to spread it evenly. Set the pan aside.

In a large bowl, combine the crispy rice cereal, Golden Grahams, and 2 cups (86g) of the mini marshmallows. Place the remaining 9 cups (387g) mini marshmallows into a separate large bowl or container.

In a large saucepan over medium heat, melt the butter until it begins to brown. Look for the butter to foam and sputter then start to show some brown bits at the bottom, about 3 minutes after it has melted.

Turn the heat to low. Add the milk powder and use a flexible spatula to incorporate, stirring constantly and making sure to clean the bottom and sides of the pan so the milk powder doesn’t burn. Cook until copper in color, about 1 to 2 minutes.

Once the butter and milk powder are browned, turn off the heat and stir in the salt, vanilla, and the 9 cups (387g) mini marshmallows. Stir to combine. Turn the heat back on low, stirring constantly, to fully melt the marshmallows, about 1 minute.

Once the marshmallows are fully melted, turn off the heat and remove the saucepan from the burner.

Add the cereal mixture to the pan and stir until fully combined.

Working quickly, transfer the mixture to the prepared pan. (It’s OK if the chocolate layer isn’t fully set.) Use the spatula to press and compact the mixture evenly into the pan; it will be very full.

Transfer the pan to the refrigerator (no need to cover) and let the Rice Krispies treats chill until the chocolate has set, about 1 ½ hours. Use the parchment sling to remove the Rice Krispies treats from the pan before slicing and serving.

Store leftover S’mores Rice Krispies Treats in an airtight container at room temperature for up to 1 week.