Bring vinegar and water to a boil with the sugar in a small pot. Add salt and stir to dissolve the sugar and salt completely. Reduce the heat to low.

Place the shallots and herbs in a food processor and pulse to finely chop. Transfer to a small plastic food storage container. Pour the hot brine over top of the shallots and herbs to cover; place a lid on the container and chill until ready to serve or let marinate at room temperature until lamb is ready to serve.