Step 1

In a medium saucepan, combine vinegar, water, sugar, and salt. Bring to a boil, stirring, until solids are dissolved. Remove from heat and add tarragon and shallot. Let stand 5 minutes.

Step 2

Meanwhile, arrange asparagus in an even layer in a baking dish. Pour brine on top. Press paper towels against surface to submerge asparagus and let stand until cooled. Transfer asparagus and brine to a large sealed container and refrigerate for up to 3 weeks.