Add butter and EVOO in your saucepan over low-medium heat.
Once the butter has melted, add your flour and whisk together. Make sure the flour is completely incorporated into the butter/oil mixture. You want to cook it for 1-2 minutes- just until the flour taste is cooked out, but not long enough for the mixture to brown.
Slowly add in your half and half while whisking. Your bechamel will begin to thicken, so keep an eye on the consistency of your sauce. If you like a thicker sauce, add less half and half, and if you like a thinner sauce, add more.
Add in your choice of cheese and stir until completely melted. The cheese will help to thicken your sauce, but you can always add a bit more half and half to thin it out.
Once your cheese has melted and you're happy with the consistency of your bechamel sauce, remove your saucepan from heat and add in your herbs/spices to taste. Depending on the saltiness of the cheese you choose to use, you may not need to add any salt, so TASTE AS YOU GO and ENJOY!