01 - Line an 8x8-inch baking dish with parchment paper, leaving enough overhang on the sides to easily lift the bars out later.
02 - In a saucepan over medium-low heat, combine the peanut butter and maple syrup. Stir continuously until the mixture is smooth and warmed through, about 2 to 3 minutes. Remove from heat and stir in the vanilla extract and a pinch of sea salt.
03 - Gently fold the lightly crushed cornflakes into the peanut butter mixture until every flake is evenly coated.
04 - Spread the mixture evenly into the prepared baking dish, pressing it flat and firmly with a spatula. Place the dish in the freezer for 20 to 30 minutes until the layer is firm and set.
05 - Remove the set peanut butter crunch slab from the dish using the parchment overhang. Cut into 16 even bars using a sharp knife.
06 - Combine the dark chocolate chips and coconut oil in a microwave-safe bowl or double boiler. Heat in 30-second intervals (or over simmering water), stirring between each interval, until the chocolate is completely smooth and glossy.
07 - Dip each bar into the melted chocolate, using a fork to turn and coat all sides evenly. Tap off excess chocolate and place each coated bar onto a parchment-lined tray.
08 - Place the tray of coated bars in the refrigerator for 15 to 20 minutes, or until the chocolate shell is fully set and firm to the touch.
09 - Transfer the bars to an airtight container and store in the refrigerator. They can also be frozen for up to 3 months.