Begin by unwrapping the caramels and placing them in a microwave-safe bowl. Add the 4 tablespoons of unsalted butter and 14 ounces of sweetened condensed milk. Microwave on high for 30-second intervals, stirring in between, until the mixture is smooth and well combined. Set aside.
In a large mixing bowl, whisk together the 2 cups of all-purpose flour, 1 cup of old-fashioned oats, 2 teaspoons of baking powder, and 1 teaspoon of salt.
In another bowl, beat together 12 tablespoons of unsalted butter and 1 cup of creamy peanut butter until combined. Add in the 2 cups of light brown sugar and mix until smooth and creamy.
To the butter and sugar mixture, add 2 large eggs and 1 tablespoon of vanilla extract. Beat until well incorporated.
Gradually add the dry ingredients to the wet mixture, mixing until just combined. A few lumps are okay.
Gently fold in the 2 cups of semi-sweet chocolate chips, 1 cup of Reese’s peanut butter chips, and 1 cup of Heath toffee bits into the cookie dough.
Preheat your oven to 350°F (175°C). Grease your 9x13 inch baking pan and spread half of the cookie dough evenly in the bottom.
Pour the prepared caramel mixture over the first layer of cookie dough, spreading it evenly with a spatula.
Dollop the remaining cookie dough over the caramel layer and spread it out as evenly as possible.
Place the baking pan in the preheated oven and bake for 25-30 minutes, or until the edges are golden brown.
Once baked, remove the pan from the oven and allow the cookie bars to cool in the pan for about 15 minutes. Then, transfer to a wire rack to cool completely before cutting into squares.
