Melt butter in stockpot; add onion and garlic. Cook over medium heat, stirring occasionally, until softened. Stir in potatoes, reserved clam juice, water, clam base and thyme leaves. Increase heat to medium high. Bring mixture to a boil. Reduce heat to medium low. Cover; cook until potatoes are tender.
Add clams, Cream Sauce Base, Worcestershire and pepper. Continue cooking until soup reaches 165°F.