Creating these indulgent S’mores Brownies with Vanilla Bean Marshmallow is straightforward if you follow these steps:

1. Preheat the oven to 350°F (175°C) and grease a 9×13-inch baking pan.
2. Prepare Brownie Batter: In a medium saucepan over low heat, melt the unsalted butter. Once melted, remove it from the heat and stir in the granulated sugar until well combined. Add the eggs, one at a time, stirring well after each addition. Incorporate the vanilla extract, mixing until smooth.
3. Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and salt.
4. Combine Mixtures: Gradually fold the dry ingredients into the wet mixture until just combined. Do not overmix.
5. Pour the brownie batter into the prepared baking pan, spreading it evenly.
6. Bake Brownies: Place the pan in the preheated oven and bake for 25-30 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.
7. Meanwhile, prepare the marshmallow topping. In a small saucepan, add the granulated sugar, corn syrup, water, and vanilla bean paste. Heat over medium, stirring until the sugar dissolves.
8. Bring the mixture to a boil and let it cook without stirring until it reaches 240°F (soft ball stage) on a candy thermometer.
9. Once the syrup is ready, remove it from heat and let it cool for 5 minutes. With a hand mixer or stand mixer, beat the mixture until it turns white and fluffy (around 5-10 minutes).
10. After the brownies are baked, remove them from the oven and allow to cool slightly (about 10 minutes).
11. Spread the marshmallow mixture evenly over the warm brownies. Top with mini marshmallows and sprinkle graham cracker crumbs on top.
12. Place the brownies back in the oven for an additional 5-7 minutes until the marshmallows are puffed and golden.
13. Remove from the oven and allow to cool completely before cutting into squares.