Balsamic Glazed Onions

I do like onions (or I certainly wouldn't have tried this recipe which includes them as not just an ingredient but pretty much the ingredient!), but it's really the balsamic glaze that sold me on it! It's not difficult, but the trimming and peeling of the onions does take time...and I only made a half recipe.

4-5 lbs small onions
(cipollini onions, white pearl onions,
red pearl onions, shallots...)
1 head garlic, separated into cloves (optional)
3 Tbls olive oil
1 Tbls fresh thyme leaves
plus sprigs for garnish
½ tsp black pepper
½ tsp coarse ground sea salt
½ C balsamic vinegar
1 C chicken or vegetable broth
1 bunch green onions
3 Tbls butter

Working in batches, add onions to a pot of boiling water; simmer 1 minute, then transfer to a colander wtih a slotted spoon and immediately rinse with cold water. Repeat with garlic.

Using a small, sharp knife, trim tips and root ends and peel onions and garlic on a cutting board; slit larger onions lengthwise (do not cut completely apart), holding your thumb against the pointy tip to keep the core from squirting out. Put onions and garlic in a bowl and drizzle with 1 Tbls oil. Stir in thyme leaves, pepper and salt, mixing to coat.

In a large skillet, heat remaining 2 Tbls oil over medium-high heat. Sautée onions and garlic, stirrign often, until most are partly browned. Add vinegar and broth; reduce heat to medium-low and simmer until onions are tender and some begin to fall apart (10-20 minutes).

Trim green onions and cut into 2" lengths. Add green onions and butter to onion and garlic mixture in skillet. Stir until well combined. Using a slotted spoon, transfer onions to a serving bowl; cover. Boil sauce over high heat until syrupy and reduced to about ¾ cup (about 4 minutes). Stir gently into onion mixture. Serve, garnished with extra sprigs of thyme.