Preheat your oven to 350° F. Line a sheet tray with a silpat or parchment, set aside.
In a large bowl, combine the oats and nuts (if using.)
In a small saucepan over low to medium low heat, stir together the peanut butter, maple syrup, and coconut oil. Heat only until melted. Once melted, remove from heat and pour over oats. Using a rubber spatula, stir mixture until everything is well coated and incorporated.
Pour the oat mixture onto your prepared tray. With your hands (and a sheet of wax paper) or a spatula, flatten and press the granola down into a tight rectangle. The key here is to press everything together as much as you can, almost like a giant granola bar. This process is what is going to give you those lovely clusters of granola.
Bake in the oven for 15 minutes. Rotate the tray and bake for 12 to 15 minutes more. Remove from the oven and allow to cool for about 10 minutes. Sprinkle with the chocolate chunks and allow granola to cool. For quicker cooling, you can place the tray in the refrigerator for 30 minutes to an hour.
Once cooled, break into clusters. You may have some bits that break off. These clusters should stay fresh for about 5 to 7 days in an air-tight container.