In a medium, heavy-bottomed saucepan over medium heat, melt butter and sugar together, stirring constantly. Add eggs and milk and whisk constantly until mixture is slightly thickened and beginning to bubble. Remove from heat and add rum and vanilla. Strain into a clean bowl to remove any bits of cooked egg. Stir in raisins and place in refrigerator to cool for 10 minutes. In a large bowl, whisk together flour, baking powder and baking soda. Add cooled raisin mixture and bring together with a fork until just combined. Divide into 12 lightly-greased muffin cups and bake at 350 for 14-15 minutes, until a tester comes out clean. Optional: brush tops of muffins with maple syrup when they come out of the oven.