Line 3 (9" x 5") loaf pans with multipurpose sealing wrap (we tested with Press 'N Seal); set aside. (Use disposable loaf pans from the grocery store, if desired.)
Microwave white chocolate morsels in a large microwave-safe bowl at 70% power for 1 minute and 15 seconds. (Morsels will not look melted.) Stir morsels until melted. Microwave again at 15-second intervals, if necessary.
Gently fold 1 1/2 cups peanut brittle and 1/2 cup peanut butter into melted chocolate, stirring until evenly distributed.
Quickly spread melted white chocolate evenly in prepared pans. Dollop 1 Tbsp. creamy peanut butter over candy mixture in each loaf pan; swirl with a knife. Sprinkle with reserved 1/2 cup crushed peanut brittle, pressing gently with fingertips. Let stand 1 hour or until firm.