Step 1

Put the vinegar, salt and pepper in a bowl and whisk until the salt dissolves, about 10 seconds

Step 2

Whisk in the mustard (if using)

Step 3

Drizzle in the olive oil, whisking constantly, until the dressing looks thick and well mixed

Step 4

Taste and add a little more vinegar if it tastes flat, or salt if it needs it, whisking after each addition

Step 5

Use immediately or transfer to a jar and store in the refrigerator for up to a month

Step 6

Shake well before using