Put sugar, butter, half & half, and corn syrup in a medium saucepan. Set pan on burner, and then turn burner on LOW.
Stir over low heat until mixture begins to boil.
Continue to cook over low heat, stirring constantly, until it reaches a full, rolling boil. (A boil that cannot be stirred down.)
Remove from heat and stir in alcohol. Step back from pan for a moment. Mixture will bubble up almost immediately and release all of alcohol. DO NOT have your face directly over the pan when you add the alcohol. All of this happens very quickly, and you can get a nasty steam burn if you stand too close.
Take the plate out of the refrigerator. Drop a teaspoon of sauce on the plate, and determine if the sauce on the plate is thick enough for your tastes.
If the sauce is thick enough for you, move on to the next step. If you would like your sauce to be thicker, return to the pan to the stove over MEDIUM-LOW. Stirring constantly, allow it to reduce for a few more minutes. Try the plate test again.
When you are satisfied with the thickness of your sauce, pour it into a clean container and allow it to cool.
Serve sauce over warm bread pudding.
Notes
Cinnamon-Orange Whiskey Butter Sauce
Use 2 ounces of cinnamon whiskey, plus 2 ounces of plain whiskey, plus 1 teaspoon orange zest.
OR, Use 2 ounces of cinnamon whiskey, plus 2 ounces of Grand Marnier.
Un-Whiskey Vanilla Butter Sauce
All of the alcohol cooks out of this sauce when made as directed. However, if you prefer not to use alcohol in your cooking at all:
Omit all alcohol
Add 1 teaspoon cinnamon when you add the sugar.
Add 1 tablespoon of vanilla when you remove the sauce from the heat.
The resulting sauce will be a much milder, but still delicious.