In a small bowl, sift the flour, baking powder and salt. Stir in the chocolate powder.
In a large bowl, cream the butter and sugar for several minutes until light and fluffy. Add the eggs, vanilla and rum extracts and beat until thoroughly combined.
Alternately stir in the flour mixture and the milk, beginning and ending with the flour.
Melt the chocolate bar chunks (either in a double boiler or microwave). Pour the melted chocolate into the batter and stir to combine.
Spoon the batter into the prepared pudding mold and secure the lid.
Place a dishtowel that's been folded several times in the bottom of the stock pot, positioning it with a long spoon if necessary. You must avoid letting the pudding mold touch the bottom of the pot and ensure that it remains standing straight throughout the steaming process. Do not let any water get into the mold.
Place the pudding mold on top of the folded towel, reduce the heat to low, cover the pot, and simmer for 1½ hours.
Remove the pudding mold from the pot and let it sit for 5 minutes while you prepare the glaze.
To make the glaze, combine the three ingredients in a small saucepan, bring to a boil and simmer for 5 minutes.
Invert the pudding onto a wire rack positioned over a cookie sheet. While the pudding is still warm, brush the chocolate glaze all over then carefully transfer to a serving plate.
Serve warm with whipped cream, hot fudge sauce, or ice cream.
To reheat, place the pudding back in the mold, cover, and boil again for a few minutes until heated.
Notes
Top quality dark chocolate is imperative to the flavor outcome of this pudding.
Recipe by The Daring Gourmet at https://www.daringgourmet.com/heritage-steamed-chocolate-pudding/