Peel the dry outer leaves of the lemongrass stalks and discard, then chop off the bottom and top ends and discard.
Slice the stalks into inch long pieces and add to infusion jar. (If you don't need to strain it because you know you're going to use it quickly, you can slice each stalk in half vertically and insert straight into the bottle. See note above).
Using a sharp vegetable peeler, peel the skin of the lemon in strips, removing as little of the white pith as possible. Add the lemon peel to the infusion jar.
Steep infused vodka for at least 24 hours and up to two weeks in a cool, dark place (a closet or a liquor cabinet is perfect).
Strain lemongrass and lemon peel by pouring mixture through a fine-mesh sieve and return infused vodka to the bottle.