Chocolate Chip Cookie Dough Bars

• 1/2 cup unsalted  butter (softened, 1 stick)
• 3/4 cup brown  sugar
• 1 tsp vanilla extract
• 2 1/4 cups all purpose flour
• 14 oz sweetened condensed milk
• 1/4 tsp salt
• 1 cup mini chocolate chips

For the Chocolate Topping:

• 1 cup chocolate chips
• 2 TBS butter
• sprinkles (optional)