First, line an 8x8 baking sheet with parchment paper and set that aside for now.
Grab a small sauté pan, and add the walnuts and pecans and toast them over low heat for about 3-4 minutes, stirring constantly until they brown. Don't let them burn! Transfer them to a small bowl and set aside.
To the same sauté pan, add the peanut butter and maple syrup and cook on medium heat for a minute or two until everything is melted, using a whisk to help things along and to avoid sticking.
To a mixing bowl, add the oats, peanut butter mixture, raisins and nuts. Give everything a good stir until fully combined.
Transfer the mixture to your prepared baking sheet, spread it out, and press into it firmly, using the back of a spoon so everything is flat and even. Refrigerate for at least 30 minutes to allow it to firm up, before slicing into bars.
Tip: Instead of walnuts and pecans, use your favorite nuts!