To make pumpkin pie spice, mix together ground cinnamon, nutmeg, ginger, allspice, and cloves in a small bowl until well blended. Use as needed and store remaining spice in an airtight container for later use.
Use 2 tablespoons butter to spread over bread slices on one side.
Place bread slices with buttered side facing up on a broiling rack. Evenly sprinkle each slice with pumpkin spice sugar.
Broil bread slices for a few seconds only until sugar bubbles up. Remove from broiler and slice each bread piece into 4 triangles.
Use the remaining butter to coat the inside of the baking dish (preferably a 6-cup baking dish 2 inches deep).
Layer the bread pieces sugared side facing up on the baking dish.
Preheat oven to 350F.
Prepare the custard sauce by placing the eggs in a 2-quart stainless steel saucepan. Whisk the eggs and add the sugar by spoonfuls until the eggs are thick and pale yellow and form ribbons in about 2-3 minutes.
Stir in the hot milk slowly in a trickle in the beginning until mixed in.
Place the eggs over moderate heat. Keep stirring slowly and constantly with a wooden spoon scraping the bottom while the custard thickens without letting it come to a boil. The custard is done when it coats the spoon in a light, creamy layer.
Stir in the vanilla extract and pour half of the custard over the toasts using a sieve. Soak the toasts for 5 minutes and then pour on the remaining custard using a sieve.
Put the baking dish on a roasting pan and place in the lower middle of the oven.
Pour boiling water in the roasting pan to fill it halfway up the baking pan.
Bake for about 25-30 minutes until done or a toothpick stuck an inch from the side comes out clean. Make sure to keep the water bath just below the simmer.
Serve warm or cold topped with a berry sauce if desired.
