In a 1-quart saucepan combine the stock and garlic. Bring to a boil over high heat, then reduce heat and simmer 2 minutes. Remove from heat.
In a 1-quart saucepan melt 4 tablespoons of the butter over high heat. Add the flour and whisk with a metal whisk until smooth, about 10 seconds. Remove from heat.
Return stock mixture to a medium heat. Gradually add the butter mixture to the stock mixture, whisking constantly until smooth. Reduce heat to very low.
Add the remaining 2½ sticks of butter, about a third at a time, whisking constantly each time until butter is melted.
Gradually add the Worcestershire, whisking constantly, and add the salt.
Continue cooking until sauce thickens slightly, about 5 minutes, whisking often.
The sauce may be kept warm (or reheated) by setting the pan over another pan of hot (but not boiling) water.
Nutritional information is based on 16 servings but does not include Basic Seafood Stock. For nutritional information on Basic Seafood Stock, please follow the link above.