Rum's richly aromatic flavor makes it a fine complement to the warm spices used in winter baking. It's an especially common addition to baked holiday treats, either as an ingredient in its own right or as the highlight of a creamy sauce. Holiday rum sauce at its best replicates the flavors of a mug of hot buttered rum. Making yours absolutely perfect is a relatively simple matter of playing with the proportions until they meet your own individual taste.
Chefs make rum sauce by caramelizing sugar, an exacting process with the potential for nasty burns if you do it wrong. With the home version, you create a similar flavor by boiling brown sugar, butter and cream or sweetened condensed milk in a saucepan. The combination of butter and cream or condensed milk should at least equal the amount of brown sugar -- a cup of sugar paired with 1/2 cup each of butter and heavy cream, for example; then simmer the mixture, stirring diligently, until it thickens slightly to a smooth, creamy texture. Add your rum during the cooking time, for a mild flavor, or at the end for more of an alcoholic bite.
The basic version of the recipe, with equal parts sugar and dairy, yields a very sweet sauce. If you like yours to have more of a creamy, buttery feel, the quantity of cream or condensed milk can be doubled or even tripled. You'll need to cook it a bit longer -- perhaps 10 minutes, instead of 5 -- before it thickens to the correct texture. Use spiced rum, or add whole spices to the saucepan, to lend the sauce additional notes of flavor. Whole spices should be strained out before serving.