Preheat the oven to 350 degrees Fahrenheit.

Lightly grease a 9"x13" pan.

In the bowl of an electric mixer, cream together butter, brown sugar, granulated sugar, eggs and vanilla. Scrape down the sides of the bowl in between and mix well.

In a separate bowl, whisk together flour, baking soda, and salt.

Add the flour mixture to the wet mixture and mix until incorporated. Quickly mix in 1 c. milk chocolate chips and pecans, if using them.

Press 3/4 of the dough mixture evenly into the bottom of the prepared pan.

Pour sweetened condensed milk over the top, then sprinkle with 1 c. milk chocolate chips.

Grab portions of the remaining 1/4 of the dough, in small amounts, and press them flat in the palm of your hand. Then lay the dough sections over the top. It's ok if it doesn't cover the whole thing, but do your best to piece it together.

Bake for approximately 21-23 minutes, or just until set.

Let cool completely at room temperature before slicing and serving.