In a small bowl, combine shallots and vinegar and let set for 15 minutes.
Add olive oil, Dijon mustard, agave, salt, pepper, and whisk or shake to combine. Adjust seasonings as needed.
Serve immediately or refrigerate in a covered container up to 5 days. If oil solidifies, let the dressing come to room temperature or microwave very briefly. Shake well before using.
Video
Notes
Make the vinaigrette tangier, sweeter, saltier or no salt, more pepper or no pepper, etc. Find the balance that's perfect for you.
Instead of Dijon mustard, you could substitute a whole grain mustard or even horseradish mustard for a spicier vinaigrette.
Don't have extra virgin olive oil? The olive oil adds such great flavor but if you're all out, substitute a mild tasting vegetable oil or grapeseed oil.