Add the Dijon and the vinegar and continue to blend. Then add the oil gradually while blending until the mixture thickens.
1 tablespoon Dijon mustard, 1 tablespoon white vinegar, 1 cup light olive oil
Add the remaining ingredients except for the milk. Blend until fully incorporated.
1 teaspoon lemon juice, ½ cup sour cream, 1 teaspoon onion powder, 1 teaspoon garlic powder, 1 teaspoon parsley flakes, 1 teaspoon dried dill, ¾ teaspoon salt, ½ teaspoon pepper
Add the milk slowly while stirring until you reach your desired thickness. (You may or may not use all of the milk depending on how thick you like your dressing.)
¼ cup milk
Notes
A food processor or immersion blender can be used in place of a traditional blender.
You can substitute ½ cup of mayonnaise for the light olive oil to save some time waiting for the oil to emulsify as you blend.
Add a pinch of cayenne pepper, a few drops of hot sauce, or a bit of finely minced jalapeño for a spicy kick.
Substitute some of the milk with buttermilk for a tangier, traditional ranch flavor.
Use fresh herbs if available (like parsley or dill); about 1 tablespoon of fresh herbs equals 1 teaspoon of dried.
Store any leftover homemade ranch dressing in an airtight container in the refrigerator. Because it contains fresh eggs and dairy, it should be kept cold at all times.
This dressing is safe to use for up to one week if the ingredients used were fresh and it is kept refrigerated, but always check for any changes in smell or texture before using.
Freezing is not recommended since the dressing may separate and lose its creamy texture when thawed.
Additional Serving Suggestions:
Make this dressing on the thick side to use as a dip with fresh vegetables, chicken wings, French fries, or mozzarella sticks.
Make this dressing a little thinner to use it as a dressing on salads.
Use as a spread on burgers, sandwiches, or wraps for an extra layer of creamy, herby flavor.