Preheat oven to 375 F and line a 9x13 pan with non-stick foil.
Combine butter and sugar.
Beat eggs and butterscotch sauce into the sugar mixture.
Add flour, baking soda, and salt, and mix until smooth.
Fold in the butterscotch chips.
Spread mixture into lined pan and bake 25-30 minutes, until a toothpick inserted into the center comes out clean. The batter is a similar color to the toothpick, so look closely!
Cool completely, then cut into squares.