In a heavy saucepan, heat the coconut milk and sugar over medium heat, stirring often, until coconut milk begins to boil. Lower heat to simmer and reduce by 1/3 to 1/2, stirring often to prevent the sugar from scorching. (If thicker, caramelized sugar begins to form on sides or bottom, use a whisk to reincorporate it.) When it reaches a similar consistency to a thick sweetened condensed milk or a drippy caramel sauce, in around 30 minutes, add 2 tablespoons coconut butter and vanilla. Stir well and remove from heat. You should end up with a little over a cup of caramel-colored, sweetened coconut milk.
Recipe adapted from She Cooks, She Cleans