In a saucepan heat the milk with the cereal until very warm but not boiling. Set aside to cool slightly
In a large bowl beat the eggs with the maple syrup, sugar, vanilla and salt.
Gradually whisk in the warm milk/cereal mixture. Start with a small amount at first so as not to "scramble" the eggs.
Butter 6-8 custard cups or ramekins. Alternatively butter a 1 1/2 quart casserole.
Stir the custard to redistribute the Grape-Nuts and pour into the custard cups or casserole. Place within a large roasting pan. Fill pan with very hot water so that it comes halfway up the custard dishes or casserole. Carefully place in the oven.
Bake the custards 10 minutes. Stir the pudding very gently to redistribute the Grape-nuts. Sprinkle the surface with the grated nutmeg.
Continue to bake until set but slightly jiggly in the middle. This will take about 20-25 minutes for the custard cups or about 40-45 minutes for the casserole.
Remove the custards from the water bath and set on a wire rack to cool. Refrigerate or serve at room temperature.