Melt butter in medium saucepan over medium heat. Continue cooking, watching closely, 5 to 7 minutes or until butter foams and turns golden brown. Immediately remove from heat. Pour butter into medium bowl, scraping bottom of pan to get all the brown bits. Let cool, stirring occasionally, until room temperature. Add sweetened condensed milk to cooled butter; stir until well mixed. Set aside. Place heavy whipping cream into large bowl. Beat at high speed, scraping bowl often, until stiff peaks form. Gently fold 1 cup whipped cream into butter mixture until mixed. Pour half of butter mixture into whipped cream; gently fold until mixed. Add remaining butter mixture and toffee bits to whipped cream mixture; gently fold until mixed. Pour mixture into two (9-by-5-inch) loaf pans or one (8-inch) square baking pan. Freeze 6 hours or until firm.