In a small bowl, whisk together rye flour, cornmeal, baking soda & salt.
In a large bowl, combine warmed molasses, milk & egg, stirring well, before adding the dry ingredients & mixing well.
Stir in the raisins.
Butter two 1-pound coffee cans, then pour the batter evenly into the two cans, before sealing the cans tightly with foil & string.
Pour 2 inches of water into a stockpot wide enough to fit the two cans, then place the cans in the stockpot, covering the pot with a lid of foil.
Turn heat to high, & as soon as the water begins to boil, turn heat to low, then steam bread for 2 hours, checking occasionally to make sure that at least 1 inch of water remains in the pot.
Remove cans from stockpot, remove foil lids & let bread cool for 20 minutes.
When cooled, with a butter knife, loosen the bread around the sides, &, holding the can upside down, shake the bread out, before slicing & serving with butter.