Baked Onions with Balsamic and Dark Ale

About This Onion Side Dish

One of our favorite ways to slow roast onions is with dark aged balsamic and nutty, sweet brown ale to balance the complex acidity of the vinegar with its malty, caramely flavors.

The resulting glorious partnership between the flavorful liquid base which infuses the onions as heat transforms them into soft, caramelized goodness is one we like to capture again and again. It is also proof of what seems to us a fundamental principle in cooking, especially within the realm of cooking with beer. 

Onions and dark beer, along with butter and thyme create a powerful, harmonious combination.

Add aged balsamic vinegar, brown sugar or beef stock and things get even better. See Porter Onion Gravy, Brats & Onions in Beer Sauce, Beersamic for more ideas.  

Ingredients

This recipe is very simple and virtually impossible to get wrong. You will need:

• onions - see below for notes on suitable varieties
• olive oil - about a tablespoon, but you can be more generous 
• butter - about ½ tablespoon sliver gets placed onto each of the halved onions to help them brown
• balsamic vinegar - use well-aged variety with depth of flavor and lower acidity
• dark ale - with low or non-detectable bitterness and pronounced caramely, roasty sweetness (less hoppy brown ales and porters make the best candidates, you can also use a lager such as bock or doppelbock)
• brown sugar - optional, use up to ¼ cup only if the beer you procured is not sweet enough; for this post we used a brown ale sweetened with maple syrup so we omitted the brown sugar altogether
• thyme, salt and black pepper - thyme is THE herb that goes best with slowly cooked onions, especially when dark ale and balsamic join the party 
• baking dish/onion baker - you do not need a special onion baker inspired dish, anything oven safe and a bit deeper (about 3 inches) and appropriately sized will do.

What Kind of Is Best for Roasting?

For best results choose a mild or sweet onion type and try to select ones that are similar in size so that they can roast evenly. We recommend the following higher-sugar content varieties:

• sweet Vidalia onions
• sweet Maui onions 
• white onions
• red onions
• yellow onions

We usually buy the onions that look the freshest and are in best shape since quality and appearance are key to the taste and presentation of this dish, especially if you'll be serving it to guests. 

How to Roast Onions (Step-by-Step)

Slow roasting onions (i.e. baking them) turns them into an appetizing, flavorful vegetable side few can refuse. The prep work is minimal and the cooking largely hands off, except for occasional basting. What you do need a bit more of is patience.

Let the onions cook for as long as they need to in order to soften and caramelize amidst the delicious liquids.

NOTE: While you can roast the onions (we suggest oven temperature of 425 F) if you are short on time, baking them as we instruct in the recipe will give you better results. Think more tender, juicier and sweeter onions petals. Plus, you will get to enjoy the aromas wafting out of the oven longer.

• Step 1. Turn your oven on to 350 F or 375 F, depending on how strong it is. To cut an onion for roasting start by cutting it in half, lengthwise. Peel the outer paper layer and the top most layer immediately underneath it. Rinse the peeled halves. Repeat with all the onions (#1 and #2 above).
• Step 2. Arrange the onion halves face up into a baking dish. (Do not be concerned if space is a bit tight initially - during baking they will shrink in size and fit better.) Drizzle with a bit of olive oil and then balsamic vinegar. (#3 and #4 above).
• Step 3. Pour the dark ale around the onion halves, place a thin piece of butter onto each half and season with salt and pepper. Add as much thyme as you'd like. You can also place a few sprigs right into the balsamic/beer liquid. 
• Step 4. Bake at 375 F for about an hour, possibly a bit longer. Start basting the onions occasionally after 30 minutes have passed. 

When Is a Baked Onion Done?

The exact time will depend on the type, size and number of onions you are slow roasting as well as your desired doneness. 

For softer, more caramelized onions allow a bit longer. If you see them browning too much for your liking and the pan juices begin to dry out you can add a couple of tablespoons of water and loosely tent the baking dish with aluminum foil. 

How to Serve Roasted Onions

Serve the onions as soon as you pull them out of the oven if you can, they do smell irresistible. Garnish with fresh thyme if you'd like and some fresh ground pepper and a few sea salt flakes are always a nice touch. 

Drizzle a bit of the juices over or around each one if plating individual servings or provide an appropriate spoon for guests to be able to do the same if serving family or buffet style. 

Recipe Variations

• apple cider - substitute apple cider vinegar and apple juice or apple cider for the balsamic and dark ale
• red wine - substitute red wine vinegar and a hearty, sweeter red wine for the balsamic and dark ale
• stock (beef, vegetable, chicken) - use stock instead of ale
• amp up the fresh herbs - use more thyme and add fresh rosemary, garlic and other herbs you like
• cheese - sprinkle some cheese (grated Parmesan or Pecorino, slice of Swiss or Gruyere) just before you take the onions out of the oven
• shallots - substitue large onions with delicate tasting shallots and bake for a couple of minutes less to account for the smaller size
• stuffed baked onion halves - brown some ground beef with spices while the onions are cooking. About 3o mins in take them out and scoop out the top few petals of each half. Place the semi-hollowed onions back in the oven. Dice the top layers as soon as you can touch them, mix them with the browned ground beef. Take the onions out of the oven again, scoop the beef mixture over them and bake until desired doneness. 

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