In a food processor blend avocado flesh, honey, lemon juice and salt until smooth.
Roughly chop chocolate if using a block. Place chocolate in a microwave-safe bowl and microwave in two 30 second bursts to melt. Mix well.
Add melted chocolate to the food processor and process until combined. To achieve a more airy texture in the fudge, chill this mixture for an hour – this step is optional.
With the machine still running, add melted coconut oil and increase speed to whip the mixture up.
Line a (24cm square or 27cm x 17cm rectangular) baking tin with baking paper allowing some paper to overhang. Using a wooden spoon scoop the mixture in and press evenly into the base and sides. Smooth the top and freeze for 4 hours.
Remove the fudge from the freezer and lift it out of the tin. Slice into squares and serve immediately sprinkled with some coconut flakes, if using.
Store any remaining pieces in an airtight container in the freezer for up to a month.