Place all the peanuts on a wide tray covered in baking paper. Make sure they're well distributed and don't touch each other for an even toasting. Place them in the preheated oven with the fan on for 10-15 minutes at 180°C. After 6-7 minutes in the oven, take the tray out and give them a good shuffle to allow the other side to toast too. Keep checking them throughout their toasting. When the peanuts start changing colour to a light brown take them out of the oven and let them cool on a cold surface. Once they've cooled down, select roughly 300g and put them in your blender. The other 100g we will use later to give our peanut butter a bit of crunchiness!
Now blend, blend, blend! Don't worry if the peanuts stay crumbly for a long time, trust the process and after about 15-20 min of blending you will have a smooth paste. To help blend the nuts into the butter, you can add a little bit of oil, a bit at a time, using more or less oil depending on how smooth you'd like your peanut butter to be. While blending you can add the salt, this is preference-based so add as much or as little as you like! If you have a tiny blender, make sure to take some breaks so it doesn't overheat.
Once the butter is all creamy and shiny, pour it into a bowl and we now lightly blend the rest of the peanuts. It doesn't need much, just a couple of pulses to get some nice crumbly granola that we then transfer to the bowl, stirring it into the peanut butter.
Once you're happy with the look of your peanut butter, spoon it into your recycled jar and enjoy! The crunchy homemade peanut butter should be stored in an air-tight container, inside a cupboard away from heat and will need to be used within about one month.