Sterilize a small jar by washing with hot soapy water, thoroughly rinsing, then filling with boiling water. Let stand, then dry with a clean cloth.
Fill the jar with thinly sliced peeled shallots.
In a small saucepan, combine vinegar, sugar and salt. Bring to a boil, then remove from heat and pour into the jar of shallots, covering them completely. Add peppercorns to the jar.
Let cool, then cover with a lid and refrigerate.
Notes
You can change the flavor of these pickled shallots simply by varying the type of vinegar or by adding different herbs or spices. I use whole peppercorns but feel free to dry different add-ins.
If you want the shallots for an Asian dish, try using rice vinegar instead.
Use equal parts of apple cider vinegar and white wine vinegar.
Add a few cracked coriander seeds for a flavor burst.
Try a pinch of dried chili flakes for a little extra heat.