On low heat in a medium-sized saucepan, melt the butter, cannabutter and chocolate until it has just about melted. Add the brown sugar, granulated sugar, salt and vanilla to the saucepan. Stir the mixture and remove from the heat as the chocolate should melt from the residual heat.
1 stick unsalted butter, 1/4 cup cannabutter, 12 oz bittersweet chocolate, coarsely chopped, 1 cup packed light brown sugar, 3/4 cup granulated sugar, 1 tsp fine sea salt, 2 tsp vanilla extract