In a saucepan over low heat melt the peanut butter chips with one cup sweetened condensed milk.
In a small saucepan over low heat, melt chocolate chips with remaining sweet and condensed milk. Remove from heat, add vanilla and stir until smooth.
Spread peanut butter mixture evenly in your lined 8x8 inch pan. Use a knife and create a swirl through the top of the fudge. Chill for 3 hours or until firm