FOR BREAD PUDDING: Heat the oven to 350 degrees F. Coat a 7- by 11-inch glass baking dish with cooking spray.

Combine 8 whole eggs, 1 1/4-cup heavy cream, pancake syrup, 1/4-cup sugar substitute, 2 teaspoons vanilla extract, cinnamon, and nutmeg in a large bowl. Stir in bread cubes; let stand for 15 minutes, tossing occasionally with a wooden spoon. Stir in walnuts.

Transfer mixture to prepared baking dish. Bake until top is puffed and golden and eggs are set, 35 minutes. Let cool slightly before cutting.

FOR CREME ANGLAISE: Combine 3 egg yolks, chocolate, 3/4-cup heavy cream, 1/4-cup sugar substitute, unsweetened chocolate, and 1 teaspoon vanilla extract in a medium saucepan over medium-low heat. Cook, stirring constantly with a wooden spoon, until the custard thickens, 6 to 7 minutes. (If the chocolate cream begins to separate near the end of cooking, whisk it vigorously off the heat to bring it back together.) Transfer to a bowl and whisk 1 minute.

Cut the bread pudding into 8 squares. Place one square on each of 8 dessert plates and spoon 2 tablespoons of the chocolate creme anglaise over each. Serve warm or at room temperature.