Preheat oven to 350°F.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter on medium speed until creamy, about 3 minutes.
Add the brown sugar and beat on medium speed until mixture is light and fluffy, about 4 minutes.
Add vanilla, egg yolk, egg, and a tablespoon of warm water on low speed and continue to mix until combined.
In a medium bowl, whisk together the dry ingredients: the flour, baking soda, and salt. With the mixer on low speed, slowly add the flour mixture to the bowl. Add the chocolates, crushed pretzels, and 1 cup of the toffee bits and mix until combined. Place the mixture into the refrigerator for at least 30 minutes.
To assemble for baking, place the graham cracker halves on a baking sheet lined with parchment paper and add a large marshmallow (or equivalent amount of mini marshmallows) on top of each half. Sprinkle ½ of the heath bar over the top of the marshmallow. For each cookie, completely cover the cracker, marshmallow, and pretzel with a cookie dough ball. You can use a cookie scoop or make dough balls with your hands.
Bake for 10 to 12 minutes or until the cookies are golden. Remove from oven and allow them to cool on a cooling rack for a few minutes before serving.