Begin with a generous amount of olive oil:
Heat it over medium-low heat. Add enough flour to turn it into goop, and fry it up into a nice roux:
Add a generous amount of minced garlic, a little Better than Bouillon, three or four good squirts of lemon juice, lots of basil (dried is fine), any combination of crushed red or ground white pepper, and a small palmful of salt.
If it thickens up very fast on contact with the moist ingredients and threatens to burn before you’ve finished adding them, you can add a little cold water and mix it in. When you’ve gotten them all into the sauce, it’s time to thin it out with cream (light and heavy both work) Don’t use milk – it will curdle! Stir thoroughly as you add cream, to make sure the roux mixture is all broken up and incorporated. Add cream a little at a time until the sauce is the right texture for your taste and purpose. Taste it; if it needs something, give it to it. If you are likely to have leftovers, add more lemon than you think you need; the strength of the lemon flavor diminishes overnight in the fridge.
Use it on pasta, veggies, as a hot dip, as a pizza sauce in place of marinara, whatever you need a yummy sauce for.