In a small bowl, mix together corn starch and water for the corn starch slurry. Set it aside for now, close at hand.
5 teaspoon corn starch, ¼ cup cold water
Pour beef drippings in a sauce pan and heat to a boil over medium-high heat.
½ cup beef drippings
Crumble up the stock cube and add to the sauce pan, then pour in water. Bring to a boil while whisking to ensure the stock cube is well dissolved.
1 beef stock cube, 1 cup water
Lower the heat to medium-low and pour in cream. Bring to a simmer.
1 cup heavy cream
Mix in the corn starch slurry and simmer 2 minutes, stirring often, until thickened.
Turn off the heat and mix in balsamic vinegar, then taste test and season with salt and pepper only if needed.
1 teaspoon balsamic vinegar
Notes
If you don't have enough drippings, replace them with double the amount of beef stock and reduce it to half. Or, make gravy without drippings instead.
Corn starch can be swapped for instant roux mix. Follow the instructions for use on the package, you probably don't need to add water.
Don't add salt until the gravy is done and you have taste tested
Make it dairy-free: use a dairy free cream alternative. Also, make sure the drippings do not contain any butter or other dairy products.
Make it the day before and heat it in a small pot on the stove over low heat
Storing: Store leftovers in the fridge in an airtight container for up to 5 days
Freezing: Let the gravy cool completely before storing it in a freezer-safe container or plastic bag. To reheat, let it thaw in the fridge overnight first.
Reheating: Pour the beef gravy into a small pot and heat it on the stove over low. You may need to add a bit of water to thin it out initially. Mix well to ensure a nice even texture before serving. You can also reheat in the microwave in 30-60-second increments, stirring in between.