Nonstick cooking spray, for greasing
1/3 cup chunky peanut butter
1/2 teaspoon vanilla extract
One 7.5-ounce jar marshmallow cream
1 cup granulated sugar
1/4 cup heavy cream or whole milk
1/2 stick unsalted butter
1 cup granulated sugar
3/4 cup heavy cream
1/2 cup light corn syrup
1/2 stick unsalted butter, cut into pieces
1 1/2 cups coarsely chopped roasted salted peanuts
2 pounds good-quality milk chocolate, coarsely chopped with a serrated knife
Use a smaller baking dish for thicker candy bars.