In a small bowl, mix the sour cream and mayonniase.
Mix in the salt, pepper, and garlic powder.
Add the blue cheese crumbles and mix them in thoroughly. Press on them to help extract their flavor into the dip.
If you'd like to thin the dip out and use it as a salad dressing, stir in water - try 1-2 tablespoons.
This dressing keeps in the fridge, in an airtight container, for up to five days. Give it another stir before serving and add a bit more water if it has thickened up while stored.For a thick and creamy dressing, it's best to use full-fat versions of the ingredients. It's also a good idea, if the sour cream has some water on top, to carefully pour it out before using.