Line 13 x 9-inch baking pan with foil. Butter foil. Sprinkle 3/4 cup peanuts over foil.
Melt butter in medium, heavy-duty saucepan over medium heat. Stir in granulated sugar, brown sugar, and corn syrup. Bring to a boil. Cook for 6 minutes (about 290° F on candy thermometer), stirring occasionally. Remove from heat.
Working quickly, carefully pour hot mixture evenly over peanuts in pan. Immediately sprinkle remaining 1/4 cup peanuts and morsels over toffee. Press down lightly before morsels begin to melt.
Refrigerate for about 1 hour or until set. Remove foil; break into bite-size pieces. Store in airtight container at room temperature.
*chilling time extra