Line your square pan with parchment paper, leaving overhang for easy removal.
In a large mixing bowl, combine the shredded coconut, oats (if using), and sea salt. Mix well to ensure even distribution.
In a small saucepan over low heat, melt the dark chocolate with butter or coconut oil, stirring constantly until smooth and glossy. Smell that rich cocoa aroma as it melts.
Pour the melted chocolate into the dry mixture, then add the sweetened condensed milk and vanilla extract. Stir vigorously until everything is well coated and sticky, with a fudgy texture.
Transfer the mixture into your prepared pan. Use the back of a spatula to press it down firmly and evenly, creating a smooth, compact layer.
Place the pan in the fridge for at least 2 hours, or until the mixture is fully set and firm to the touch. The surface will look glossy and feel slightly tacky.
Once chilled, lift the set mixture out of the pan using the parchment overhang. Slice into squares or rectangles about 2cm thick, pressing gently if they crack.
If desired, melt a little extra chocolate to drizzle over the top or sprinkle toasted coconut for decoration. Chill again for 15 minutes to set toppings.
Serve the bars straight from the fridge for a chewy, fudgy bite. Keep leftovers in an airtight container in the fridge for up to a week.
