Special equipment: heatproof spatula, candy thermometer
Spray a 13-by-9-inch baking dish with nonstick spray and line with parchment paper, leaving 2 inches of overhang on each side.
For the nougat: Combine the peanut butter, vanilla and marshmallow cream in a large mixing bowl and reserve. Combine the sugar, cream and butter in a small heavy-bottomed saucepan over medium-high heat. Stir with a heatproof spatula until the sugar dissolves. Fit the saucepan with a candy thermometer and continue monitoring until the mixture starts to turn a light amber color and the temperature reaches 250 degrees F, 4 to 5 minutes.
Once your nougat hits 250 degrees F, remove from the heat and add to the marshmallow mixture. Mix together to completely combine, but don't overwork. The mixture should be light and fluffy. Turn out the nougat into the prepared pan and spread evenly with a rubber spatula coated in nonstick spray. Place in the refrigerator to cool and get going on your next layer, the caramel.
For the caramel filling: Add the sugar, cream and corn syrup to a heavy-bottomed saucepan over medium heat. Carefully stir to combine with a heatproof spatula until the sugar dissolves and bring the mixture to a boil. Stop stirring and boil until the mixture begins to turn an amber color and reaches 250 degrees F, 8 to 10 minutes. Remove from the heat and stir in the butter, carefully, as it will foam up. (Adding the butter at the end will stop the cooking and keeps your caramel soft and chewy.) Keep stirring until it's all dissolved, and then stir in the peanuts. As tempting as it may be, never stick your finger in hot caramel to taste, sugar burns and hurts!
Pour the caramel over the nougat and spread evenly with the spatula. Place in the refrigerator until the caramel is completely cool, 15 minutes.
Transfer the candy to a cutting board. Cut lengthwise into thirds and then across in nine 1-inch rectangles, using a sharp knife that has been sprayed with nonstick spray. You can mark the caramel nougat with your knife as a guide before cutting out your bars.
For the chocolate: Melt the chocolate in a heatproof bowl set over a pan of simmering water. Stir occasionally until the chocolate has melted and is smooth, 8 to10 minutes. Dip each candy piece and completely cover with chocolate on all sides, using two forks, allowing the excess to drip off. Place on a wire cooling rack for the excess to drip off while you dip all of the bars. Once the bars are dipped, transfer to a parchment-lined baking sheet and allow the chocolate to set in the fridge at least 20 minutes.
Use a smaller baking dish for thicker candy bars.