Toast the white sesame seeds on a dry pan until fragrant and slightly golden brown. Do the same with the peanuts. Let them coold down. You can do this few days before too. I get store-bought roasted peanuts and toasted sesame seeds and so I skip this step
Roughly chop the peanuts into smaller pieces or use rolling pins or food processor to break them into smaller pieces, but not into powder
Place chopped peanuts, salt, and sesame seed in a mixing bowl. Stir to mix
Get things ready before cooking the sugar:
Get a chopping board, knife sprayed with cooking spray or rub some oil on it, 2 large parchment papers , a rolling pin ready. The sugar hardens very quickly and so we need to get things ready
Place 1 of the parchment paper on the cutting board, greased side up. We are going to pour the brittle here later on top of the parchment. The other parchment paper will be placed on top of the brittle so that the rolling pin will not stick to the brittle
Cooking the sugar syrup:
Get a small saucepan that has a glass lid. Put sugar, water, and vinegar in a small saucepan (that has a glass lid if possible) and cook over low heat until sugar started to melt
Close the lid and increase the heat to medium. The sugar will continue to cook and bubbles and slowly turning into a light amber color, about 10-12 minutes
Test the sugar using cold-water method:
Scoop a tiny amount of the syrup and drop it into room temperature water. Let it cools down a bit and pick up the syrup and it is hard and will not bend. This is the "hard crack" stage, which is suitable for brittle. If you have a candy thermometer, it is about 300° F–310° F. That's what makes the brittle hard and crunchy. Turn off the heat and stir in the peanut sesame mixture until they are coated with the syrup
Shaping and cutting:
Carefully and quickly pour and spread this mixture on top of the greased parchment paper you prepare earlier, cover with another piece of parchment paper, greased side down. Use a rolling pin to quickly flatten the brittle into one layer, about 1/2-inch thickness
Use a knife to cut into the desired size when they are still warm. They are hard to cut and will break into small pieces if you cut them when they have cooled down completely. They will still appear a bit softer because they have not cooled down completely
Let them cool down completely over a wire rack and then store in an airtight container and they can be kept for up to 1 month