Step 1: Line an 8×8 inch square baking pan with parchment paper, leaving a slight overhang on two sides for easy removal.
Step 2: In a large mixing bowl, combine the rolled oats, chopped nuts, and sea salt. Stir well to distribute the ingredients evenly.
Step 3: In a microwave-safe bowl, combine the peanut butter and honey. Heat for 30-45 seconds until melted and smooth, then stir in the vanilla extract.
Step 4: Pour the warm peanut butter mixture over the dry oats. Mix thoroughly with a spatula until all the oats are well-coated and the mixture is sticky.
Step 5: Fold in the mini chocolate chips. (Note: if the mixture is too warm, the chips may melt slightly, which creates a lovely marbled effect).
Step 6: Transfer the mixture to the prepared baking pan. Spread it evenly and use a flat-bottomed object to press down very firmly.
Step 7: Refrigerate the pan for at least 2 hours, or until the block is completely firm.
Step 8: Lift the block out of the pan using the parchment paper overhang. Use a sharp knife to cut into 12 even granola bars.