Saute onion in nonstick pan over medium heat.
Add 1 Cup water, potatoes, clams and chicken bouillon. Simmer until potatoes are tender, about 10 minutes.
Blend 1/2 Cup water with flour and cornstarch in blender (add salt and pepper to taste). Add this mixture to soup mixture slowly, whisking in well.
Cook over medium heat, stirring constantly until thickened.