Step 1

Combine the olive oil and balsamic in a jam jar or other container with a good-sealing lid. Add a big pinch of salt and a few grinds of black pepper. Screw on the lid and shake vigorously. Dip a piece of lettuce into the vinaigrette and taste. Adjust the salt, pepper, or the proportion of oil and vinegar to taste.

Step 2

This vinaigrette will keep on the counter for several weeks (refrigerate if you added any fresh ingredients). The oil and vinegar will separate a few minutes after shaking — shake to recombine before dressing your salad.