4-Ingredient Peanut Butter Cookies

This is one of my old recipes, so I don't have a picture. These are quick and easy and made with 4 simple ingredients that everyone has in their kitchen. They're nice and chewy and I even stirred in a bit of cocoa powder into half of the batch, so they tasted a bit like Reese's Peanut Butter Cups! 
1 cup peanut butter + 1 cup sugar + 1 teaspoon vanilla + 2 egg whites, mixed, dropped on a baking sheet and baked at 350 F for 10-11 minutes. 
Just be careful not to burn them, as some of mine did.  
Try making these for a snack, picnic or party.
If you want a good peanut-buttery flavour, then these are for you!