Preheat the oven to 350 °F (176.67 °C). Spread peanuts in an even layer and toast for about 10 minutes. Don’t leave them in too long, or they could burn and become very bitter.

In a large stainless steel saucepan, pour in the molasses and bring to a boil. Cook over moderately high heat, occasionally stirring, until the caramel is thick with tight bubbles and registers 245⁰F-250 °F on a candy thermometer, about 10 or 15 minutes.

Since the molasses give the mixture a dark color, it’s hard to tell if it’s reached the firm ball stage. I’d highly recommend the use of a candy thermometer, or you can use the water test:

Drop a little of this syrup in cold water, and it will form a firm ball, one that won’t flatten when you take it out of the water but remains malleable and will flatten when squeezed). Stir in the peanuts and continue cooking and stirring until it begins to thicken.

Add the ground peanut and continue cooking until the becomes golden brown or reaches a hard crack stage, 300⁰-310⁰degrees F.

Remove and immediately scrape the Dulce de Mani onto a buttered 9×5 loaf pan baking sheet. Using the back of a silicone spatula or spoon (oil it lightly if it sticks), spread the brittle into a thick or thin, even layer. Work fast.

Use a sharp chef's knife to cut the brittle while it is still warm. Letting the brittle cool too much before spreading can affect the texture. Let cool completely, about 30 minutes. Transfer to a sealed container and keep it in a cool, dry place