Preheat the oven to 300°F/150 °C and set an oven rack in the middle position. Line a baking sheet with parchment paper.

In a wide saucepan, mix the peanuts, maple syrup, salt and cayenne (if used). Stir well allowing the liquid to come to a low bubbling (on the stovetop). Keep the temperature low to avoid burning and stir every now and then. At a certain point, the liquid (maple syrup) starts to evaporate, keep on stirring until no more liquid is visible, you will notice that it starts to crystalize and look like little flecks of sugar on the peanuts, this is an indication that it is time to remove from stovetop. The process takes about 20 minutes. Directly, transfer to the lined baking sheet, and keep to cool down. You can enjoy them directly, but after testing, I found that baking them for further 20- 25 minutes over low heat will yield extra crunchy candied peanuts. Make sure to check before the mentioned time, simply because ovens are different.

Bake for about 25- 30 minutes, stirring every a few minutes. Watch closely to prevent the peanuts from burning. Remove from the oven and set aside to cool down a bit. Use your hands to break apart the clumps before storing.