Line a large baking sheet with foil. Preheat the oven to 325ºF.
In a large saucepan, combine the sugar, butter, and cornstarch. Place over medium heat and cook, stirring constantly, until the butter melts. Bring the mixture to a boil and let it boil for 1 minute.
Remove from the heat and stir in the cinnamon, nutmeg, and salt. Once combined, stir in the peanut.
Carefully spread the mixture onto the prepared baking sheet. (Be careful, as it is very hot. Use a spatula - do not attempt to use your hands.)
Place the baking sheet in the oven and bake for about 20 minutes, stirring every 5 minutes. The mixture will melt and spread out - it is supposed to do that.
Once the 20 minutes are over, it should be golden brown. Remove from the oven and allow the toffee peanuts to sit until completely cooled.
Break into pieces to serve.
