In a 2-gallon stockpot cook onion and celery in bacon grease (or oil) until translucent.
Pour in chopped clams in juice, clam juice, diced potatoes, Tabasco, thyme, basil and white pepper. Mix well and bring to a simmer over medium heat for 5-10 minutes.
Add half & half and increase heat until a slow boil begins.
Slowly add roux mixing well. Keep mixing until well incorporated.
Reduce heat and simmer for 15 minutes.