Puree cucumber and garlic in food processor. Place puree in a fine mesh strainer, press down gently with a spoon and let drain. (Cucumbers are largely water, so if they are not well drained, the dressing will be too thin)
Place remaining ingredients in food processor and blend together
Add pureed cucumber and garlic. Mix together. If too thick, thin with a little water, a teaspoon at a time. Refrigerate for an hour (or longer) before serving.