Line a mini muffin pan with 12 waxed or silicone muffin liners.

In a small saucepan, mix together the maple syrup, cashew butter and coconut oil over medium heat. Add salt, if using (starting off with 1/8 teaspoon and adding more, if needed). At first it might not appear to come together well but be patient.

Stirring constantly, bring to a boil and while continuing to stir constantly, boil for about 2 minutes. It should have thickened a bit and become glossy. If it hasn't, boil for up to another minute. If you use a heavy bottom pan, you may need to boil it a little longer. Stir in the vanilla until well combined.

Pour into the liners and place the pan in the freezer. If you don't have room in your freezer, refrigerate for a few hours until firm and then transfer the fudge pieces to a small container that does fit in your freezer.

Freeze / chill until the tops are no longer runny, top with flaky sea salt and return to the freezer.

Freeze for about 2-3 hours. The liners will be easy to remove once the fudge has thoroughly frozen. They'll stick if you try to remove them too early. Store in the freezer for up to 3 months or the refrigerator for 1 month. If storing in the freezer, defrost for about 10-20 minutes at room temperature.