Mars Bars Squares

Crust:
1 c butter
1/4 c shortening (Crisco)
1/2 tsp vanilla
1/2 c powdered sugar
1 1/2 c flour
Beat & spread in 9x13 pan.
Bake @ 350 for 5-10 minutes.

Caramel:
1 c butter
1 c brown sugar
1/4 c corn syrup
1 c sweetened condensed milk (not whole can!!!)
Melt butter, add other ingredients. Bring to boil on medium heat, stirring constantly. Boil 5 minutes. (The recipe says to beat with an electric beater for 5 minutes, but I don't)
Pour over the crust.
Sprinkle with 1 c chocolate chips while caramel is still hot. Spread.
Refrigerate. Use warm knife to cut into squares or chocolate will crack.