Start by preheating your oven to 350°F (175°C). Prepare an 8x8-inch baking pan by lining it with parchment paper, allowing some extra paper to hang over the sides for easier removal later.
In a large mixing bowl, combine the rolled oats, ground flaxseed (if using), chopped nuts, and a pinch of salt. Stir everything together until evenly mixed.
In a separate microwave-safe bowl, gently warm the natural peanut butter and honey (or maple syrup) in the microwave for about 30 seconds, or until they are warm and slightly runny. After warming, mix in the pure vanilla extract until well blended.
Carefully pour the warm peanut butter mixture over the oat mixture in the large bowl. Using a spatula or wooden spoon, mix everything thoroughly until all the dry ingredients are fully combined with the wet mixture.
Gently fold in the dark chocolate chips, ensuring they are evenly distributed throughout the mixture without breaking them.
Transfer the mixture into your prepared baking pan. Using a spatula or your hands, firmly press it down to create a compact and even layer across the bottom of the pan.
Bake in your preheated oven for 15-20 minutes, or until the edges are set and a light golden color appears. Keep an eye on them to avoid over-baking.
Once baked, remove the pan from the oven and allow it to cool for at least 10 minutes in the pan. Use the overhanging parchment paper to lift the energy bars out of the pan.
Allow the bars to cool completely on a cutting board. Once cooled, cut them into bars of your preferred size, whether small snacks or larger servings.
Store the energy bars in an airtight container in the refrigerator for up to a week, or you can freeze them for longer storage, keeping healthy snacks on hand for weeks to come.
Notes
For a delightful touch, consider drizzling some melted chocolate on top of the bars before serving, or sprinkle a few extra chopped nuts for garnish.