Place all ingredients except the oil in a small dish with deep sides, or in a mason jar. Whisk well.
Drizzle in the oils slowly, while steadily whisking, to ensure the oil and vinegar emulsify.
Taste, and adjust for salt and pepper. One of the best ways to taste a dressing is with a piece of lettuce so you can understand how the dressing will taste in the dish. Careful when tasting that you get an accurate mix of oil and vinegar in your bite. Dip deep into the dressing to avoid getting mostly oil, as the oil tends to rise to the top. Store dressing in a glass mason jar or bottle.
Shake well before use. Use a ladle or spoon, rather than pouring the dressing to ensure an equal distribution of oil and vinegar in the salad.