Prepare the Ingredients: Measure out all your ingredients beforehand. This is important as the process can move quickly once the sugar carmelizes.
Combine Sugar and Corn Syrup: In a large bowl, air fryer safe bowl, combine the granulated sugar and corn syrup. Stir until just combined.
Place the bowl into the air fryer, set the air fryer temperature to 310 degrees F, and set the cooking time for 4 minutes.
Add Peanuts: Carefully remove the bowl from the air fryer (it will be very hot and stir in the roasted peanuts and butter.
Return the bowl to the air fryer and cook for 3-5 minutes or until the mixture turns a deeper amber color. Watch carefully to avoid burning.
Final Ingredients: Quickly stir in the baking soda and vanilla extract. The mixture will bubble up when the baking soda is added.
Spread the Brittle: Immediately pour the mixture onto a baking sheet lined with parchment paper or a silicone baking mat. Spread it into a thin layer using a spatula.
Cooling: Allow the brittle to cool completely at room temperature. This will take about 30 minutes.
Break Into Pieces: Break the brittle into pieces once cooled and hardened.
Serve and Enjoy: Enjoy your homemade peanut butter brittle as a sweet snack or a treat.