Preheat the oven to 350° F (180°C). Spray a 9x13 pan with non-stick spray and set aside.
In the bowl of a stand mixer or with an electric hand mixer, cream together the butter, brown sugar and granulated sugar until light in color and fluffy in texture. This will take about 2 minutes.
1 cup (222g) salted butter, 1 cup (246g) brown sugar, 1/2 cup (115g) granulated sugar
Scrape the sides and add in the egg and vanilla. Mix until well combined.
1 egg, 1 tsp vanilla
Next, add the flour, baking soda and salt. Mix until a soft dough forms.
2 1/4 cup (342g) all-purpose flour, 1 tsp baking soda, 1/2 tsp salt
Now you will add in all of the mix-ins– the milk chocolate chips, chocolate chunks, pretzels and toffee bits, and mix until evenly distributed.
1 cup (200g) milk chocolate chips, 1 cup (200g) semi sweet chocolate chunks, 3/4 cup (45g) crushed pretzels, 3/4 cup (132g) toffee bits
Finally, press the dough into the prepared 9x13 pan and sprinkle the top with sea salt.
flakey sea salt, for garnish
Bake at 350°F (180°C) for 15-17 minutes or until the edges and the top begin to turn golden brown.
Allow the bars to cool completely before cutting. Enjoy!