You can substitute bourbon with any liqueur you prefer, such as rum, brandy, or Irish cream.
If you prefer a non-alcoholic version, omit the liquor and double the amount of vanilla extract.
This sauce will thicken as it cools. If reheating, do so gently over low heat, stirring frequently, to avoid curdling the eggs.
Store leftovers in an airtight container in the refrigerator for up to 3 days.