If you use pre-roasted peanuts, you can skip steps 1 & 2. If you need to toast raw blanched peanuts, place them in a flat pan over medium heat on the stove. Stir the peanuts in the pan until slightly browned and toasted, which should take about 10 minutes.
Alternatively, to roast a larger batch (approximately 1 cup) in the oven, arrange the peanuts in a single layer on a baking tray lined with parchment paper. Roast them in a preheated oven at 350°F for about 15 minutes.
Add your roasted peanuts to a food processor and pulse them a few times to chop them into small pieces. Transfer the chopped nuts to a plate or bowl and set aside.
Preheat oven to 350°F and line a baking tray with parchment paper. Add all the ingredients, except the roasted peanuts, to a food processor and pulse the mixture a few times, stirring the mixture between pulses.
Continue pulsing until the mixture resembles grainy, crumbly sand, which you can sieve quickly through your fingers.
Transfer the mixture to a parchment-lined baking tray and bake in a preheated oven for 7 to 10 minutes at 350°F. Stir occasionally to prevent the mixture from burning.
Switch off the stove, remove the tray, and allow the crumb topping to cool in the tray.
Once the peanut butter crumb topping has cooled, add the chopped roasted peanuts to the mixture. Stir well to combine everything.
Then, hold the edges of the parchment paper to lift the mixture and transfer it into a storage jar, using the paper as a funnel.