Combine the peanut butter, sugar, and vanilla in a mixing bowl. Stir vigorously with a spatula until the mixture is smooth, slightly fluffy, and well combined, about 2 minutes. The mixture should be creamy and fragrant.
In a small saucepan over low heat, melt the butter gently until just bubbling and fragrant, about 2-3 minutes. Be careful not to burn it.
Pour the melted butter into the peanut butter mixture. Stir thoroughly until the butter is fully incorporated, creating a rich, glossy texture.
Add the rolled oats to the wet mixture. Fold them in with your spatula until all oats are evenly coated and the mixture becomes thick, sticky, and easy to scoop.
Line a tray with parchment paper to prevent sticking. Using a spoon or cookie scoop, portion out the mixture and shape into small, rounded cookies about 1-2 inches wide.
Gently press each cookie with the back of a spoon to flatten slightly. This helps them set evenly and creates a more attractive shape.
Let the cookies rest at room temperature for at least 30 minutes until they firm up and develop a crackly surface. For faster setting, refrigerate for 15 minutes.
Check the cookies: they should be firm to the touch, with a slight crackle on the surface and a chewy center. Once set, they’re ready to enjoy or store.
