Add a tablespoon of olive oil to a medium saucepan or skillet over medium heat. When the olive oil starts shimmering, add the chopped onion, a small pinch of salt, and ground black pepper and cook, stirring occasionally for 5 to 7 minutes. 

Once the onion is softened and starting to brown a little, add 2 tablespoons of butter and allow it to melt. 

When the butter is melted, add 2 tablespoons of flour and stir it with all the butter and onions. Allow the flour to cook for about 1 to 2 minutes. 

After 1 to 2 minutes, add 1/2 cup of chicken/vegetable stock and 1/2 cup of heavy cream to the pan. Stir everything to start the creamy gravy. 

In a minute or two, everything should start to thicken and the gravy should be almost ready. Taste it now to test for seasoning and if you think it needs more salt or ground black pepper, add stir and serve.