1Combine olive oil, mustard, vinegar, salt, and pepper in a Mason jar or container with a tight-fitting lid; cover tightly with the lid and shake vigorously until thickened, about 2 minutes. Taste dressing and adjust flavor with salt and pepper.
Footnotes
Cook's Note:
If you find your mustard gets stuck at the bottom of your Mason jar, you can use a small spatula or whisk to mix it before shaking.