Stir the tahini well before measuring, as the solid pulp and the oil separate in the glass. Put the tahini in a bowl, first add the water and lemon juice in a thin stream and stir constantly. The sauce is often a bit thick at first, but it becomes creamier and white. Season to taste with salt, garlic and pepper. Arrange in shallow bowls and sprinkle with paprika and parsley. If it is too thick, use a little more water.