01 - Line an 8x8-inch baking dish with parchment paper, leaving overhang on the sides for easy removal.
02 - In a saucepan over medium-low heat, combine the peanut butter and maple syrup. Stir continuously until smooth and warmed through, about 2 to 3 minutes. Remove from heat and stir in the vanilla extract and sea salt.
03 - Gently fold the lightly crushed cornflakes into the peanut butter mixture until every piece is evenly coated.
04 - Transfer the mixture into the prepared baking dish and spread it evenly, pressing down firmly with a spatula to create a flat, compact layer. Place the dish in the freezer for 20 to 30 minutes until firm.
05 - Remove the set slab from the pan using the parchment overhang and 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, stirring between each, until completely smooth and glossy.
07 - Dip each bar into the melted chocolate, turning to coat all sides evenly. Allow excess chocolate to drip off, then place each coated bar onto a parchment-lined tray.
08 - Refrigerate the coated bars for 15 to 20 minutes, or until the chocolate shell is fully set and firm to the touch.
09 - Transfer bars to an airtight container and store in the refrigerator. They can also be frozen for up to 3 months.