In a medium or large sauce pot (one big enough for you to use your mixer in), mix together the chopped chocolate and coconut milk. Turn the heat to low and while stirring occasionally, melt the mixture.
1 2/3 cups (283 grams) semi-sweet chocolate, 1 cup (240 ml) canned full-fat coconut milk
When no more lumps remain, stir in the salt (I like 1/4 teaspoon but you may want less). Place the pot on a trivet and put in the refrigerator to chill for 1 1/2 - 2 1/2 hours or until the mixture is cold and has thickened quite a bit (so that it's no longer pourable).
1/8 to 1/4 teaspoon salt
Remove the chilled ganache from the refrigerator and using an electric mixer (you could also transfer it to a stand mixer), beat the ganache until light and fluffy, about 2 minutes.
If making an 8" cake - spread about 2/3 cup of frosting between the two layers of cake, 1/2 cup on top and the remaining on the sides. There's about 2 cups of frosting. The frosting is stable at room temperature and doesn't melt but should be kept refrigerated (it's fine to keep the cake out for about 8 hours at room temp). Keeps refrigerated about 4-5 days.