Butter the bottom and sides of a 10 x 15 inch baking pan with 1 1/2 teaspoons
of butter.
Sprinkle with 1 cup peanut butter chips: set aside.
In a heavy saucepan, bring sugar, corn syrup, water and remaining butter
to a boil over medium heat, stirring constantly. Cook and stir until butter
is melted. Cook, without stirring, until an candy thermometer reads 300
degrees. (hard crack stage).
Remove from heat: stir in peanuts. Quickly pour onto prepared baking pan.
Sprinkle with chocolate chips and remaining peanut butter chips.
With a knife, gently swirl softened chips over top of brittle. Cool before
breaking in pieces.
Store in an airtight container. Yield about 2 1/2 pounds.