1. Melt the butter in a small saucepan over medium heat. Stir in the dark brown sugar, heavy cream, and fine sea salt. Cook, stirring often, just until the mixture is smooth and tiny bubbles appear around the edges, 2–3 minutes. Remove from the heat and let cool for about 10 minutes.

2. Transfer the cooled brown sugar mixture to a mixing bowl and stir in the vanilla extract. Gradually add the powdered sugar, mixing until thick and smooth.

3. Add the graham cracker or digestive biscuit crumbs, toffee bits, and chopped pecans (if using). Stir until everything is evenly combined and the mixture forms a soft dough that holds together when pressed. If it feels too sticky, add a bit more crumbs; if too dry, add a teaspoon of cream.

4. Cover the bowl and refrigerate for 45–60 minutes, or until the mixture is firm enough to scoop and roll into balls without sticking badly to your hands.

5. Line a baking sheet with parchment paper. Use a small cookie scoop or spoon to portion the dough into 1-tablespoon mounds. Roll each portion between your palms to form smooth balls and place them on the baking sheet. Freeze for 20–30 minutes, until firm.

6. Place the semi-sweet chocolate and coconut oil or neutral oil in a heatproof bowl. Melt in the microwave in 20–30 second bursts, stirring between each, until smooth and glossy, or melt over a double boiler.

7. Working with a few truffles at a time, use a fork to dip each chilled ball into the melted chocolate, turning to coat. Tap off the excess chocolate on the side of the bowl and return the truffle to the parchment-lined baking sheet. Immediately sprinkle with extra toffee bits and flaky sea salt, if using.

8. Refrigerate the tray for 20–30 minutes, until the chocolate is fully set. Transfer the truffles to an airtight container and store in the refrigerator until ready to serve.