In a medium sized saucepan, melt the butter over medium heat. Once melted, keep cooking it while stirring frequently, and the butter will begin to sizzle and foam before it starts to brown. Once it has turned an amber brown color, remove from the heat and pour into a small bowl. Place the butter in the fridge to cool down while we make the rest of the dough.
Add the graham cracker crumbs to the same saucepan and toast them over medium heat, stirring gently to ensure they don't burn. Toast until they are darkened, about 5 minutes, before transferring to a small bowl to cool.
Preheat the oven to 350℉ and line two baking sheets with parchment paper or a silicon baking mat.
In a medium sized mixing bowl, whisk together the flour, oats, baking soda, cinnamon, and salt. Set aside.
In a large mixing bowl, whisk together the slightly cooled brown butter, granulated sugar, brown sugar, and espresso powder. It won't fully combine yet, but that's ok! Whisk in the eggs one at a time, followed by the vanilla extract. The mixture should be smooth now. Add in the dry ingredients and toasted graham cracker crumbs and use a large spatula to fold together the dough. Finally, fold in the pretzel crumbs and dark chocolate. The dough will be a little greasy.
Using a large cookie scoop, shape the dough into balls, somewhere between 1-2 Tablespoons in size. Place on the previously prepared baking sheet roughly 2 inches apart. Bake for 12-14 minutes or until the cookies appear set in the center and browned lightly on the sides.
Let the cookies cool for 10 minutes before enjoying warm. Cooled cookies stay fresh for up to 5 days sealed in an airtight container at room temperature.
