Line a small loaf tin or container with baking paper for easy removal. Soak your dates in boiling water for at least 5 minutes to soften, then drain well.
Add the pitted dates, nut butter, vanilla extract and sea salt to a food processor or high-speed blender. Blend until smooth and sticky. If the mixture is too thick to blend, add 1-2 tablespoons of milk as needed.
Scrape the caramel mixture into your prepared tin. Press it down very firmly and evenly using a spatula or clean, damp hands. Freeze for 20-30 minutes, or until firm.
Once set, lift the caramel slab out of the tin and slice it into small squares or rectangles using a sharp knife.
In a heatproof bowl, melt the dark chocolate and coconut oil, if using, in the microwave in 20-second bursts, stirring between each one until smooth. Alternatively, melt gently over a double boiler.
Use a fork to dip each caramel square into the melted chocolate, allowing the excess chocolate to drip off. Place on a parchment-lined tray. Sprinkle with flaky sea salt before the chocolate sets, if desired.
Place the dipped caramels in the fridge for 10-15 minutes, or until the chocolate is set.