WHAT YOU'L NEED
1/2 cup white sugar
1/2 cup brown sugar
3/4 cup (1 1/2 sticks) unsalted butter, divided
3/4 cup flour
2 cups quick cooking oats
1/2 tsp baking soda
1/2 tsp kosher salt
1/2 cup sweetened condensed milk
1 cup chocolate chips
2 tsp vanilla, divided
3 Tbs bourbon*
Flaky Salt for sprinkling, optional
*If you aren’t a bourbon fan, coffee liquor would be a good substitute
WHAT YOU'LL DO
First, take 1/2 cup (1 stick) of the butter and put it in a smallish skillet (you want more surface space than height) on medium heat. Melt the butter and swirl the pan occasionally. You will see it start to change color from yellow to a very light amber and the milk solids will separate from it and then it will start to foam. Turn the heat to low and watch it closely and remove from heat as soon as the milk solids or “bits” on the bottom start to burn and the butter is a light caramel color. Strain your brown butter through a fine mesh sieve (or don’t, if you really like the flavor of those burnt bits!) into a small bowl and put in the fridge to cool slightly. Wipe your pan out with a paper towel and set aside— you’ll use it again and theres no need to wash it.
Preheat your oven to 350 degrees F. Prep an 8x8 square baking dish by lining it with parchment, leaving two of the edges longer to form “handles” to help you lift the bars out later. Spray lightly if desired.
Mix your egg and both sugars in a medium sized mixing bowl until fluffy and lightened in color. Drizzle in your brown butter (hopefully slightly cooled at this point) slowly and beat to combine. In a small, separate bowl mix your oats, flour, salt, and baking soda. Then slowly add in your dry mixture to the wet.
Spread about 2/3 of this mixture on the bottom of the prepared dish, pressing it down into an even layer with your fingers or the back of a spoon.
Next, melt the remaining 1/4 cup (4 Tbs) butter, sweetened condensed milk and chocolate chips in your pan on medium-low heat and stir until smooth and glistening. If the mixture starts to bubble, turn the heat down to low. Once completely melted and smooth, remove from heat and stir in your vanilla extract and bourbon.