Maple adds a wonderful dimension to this already-delicious dessert, made even richer by the addictive toffee sauce.
Preheat oven to 325°. Butter a 9x9-inch glass baking dish. Toss bread with 3 tablespoons melted butter. Toast in oven until bread just starts to brown, 10 minutes; stir bread occasionally to toast evenly. Remove and place in a large bowl to cool. Whisk remaining melted butter, eggs, yolks, cream, maple syrup, spices, and salt together. Put bread and raisins into a gallon zip-top bag and add egg mixture. Squeeze the air out of the bag and seal; then use your hands to work egg into bread. Let soak 15 minutes; then pour into prepared baking dish. Bake until custard is set and top is nicely browned, about 50 minutes. Cool slightly; serve with warm rum-spiked maple-toffee sauce (recipe below).
In a small saucepan over medium heat, melt butter. Add brown sugar; increase heat to medium high and stir until sugar dissolves. Add maple syrup, cream, and vanilla; simmer 10 minutes, stirring often. (Mixture should thicken slightly.) Remove from heat, add rum, and let stand 5 to 10 minutes; sauce should thicken slightly again as it cools. Serve over warm bread pudding.