Onion Jam Recipe (Caramelized)

🔪 Get out your mandoline

A mandoline really does the job: your onions come out thin, even and consistent, from the first slice to the last. It’s not just about looks. Slices that are all the same cook at the same speed, so you don’t end up with burnt bits next to bits that are still crunchy. A knife works too, just take your time and keep your slices as thin as you can.

🔥 Low heat, and no lid

I never make my caramelized onions with a lid. The lid keeps the water in the skillet, and your onions boil in their own juices instead of caramelizing. Leave them uncovered, over medium-low heat, and stir often. They should melt slowly, not sear: if they brown too fast, your heat is too high, turn it down right away.

💧 If it sticks to the bottom

Add a small splash of water and scrape the bottom with your wooden spoon. Everything stuck there is flavor, and the water lifts it back into your onions. Go a little at a time: the goal is to loosen, not to drown. I didn’t need any, but if your skillet sticks more than mine, that’s how you save it.

🥃 Dark rum or port

I used dark rum, and I thought it was amazing. You can also use port, depending on what’s in your cupboard. It’ll change the flavor a little, port is fruitier, but both make a great onion jam. Let it reduce a good two minutes while you scrape the skillet, so the alcohol taste cooks off and only the good stuff stays.

🍁 Maple and balsamic, no fuss

Whatever maple syrup you have does the job, no matter the grade. For the balsamic, I used a regular grocery store vinegar. Personally, I’m not as into the thicker balsamic, but that’s really a matter of taste. That duo is what gives the jam its sweet and slightly tangy side, the one that goes so well with a rich cheese.

🥄 How you know it’s ready

Drag your spoon across the bottom of the skillet: if it leaves a trail that stays open for a second before the jam fills it back in, it’s ready. The liquid should be syrupy, not watery at all. Don’t wait for it to get thick like taffy in the skillet, because the jam keeps thickening as it cools. Reduced too far, it turns hard in the fridge.

🧀 My favorite holiday combo

A little toasted bread with a drizzle of olive oil and spices, a spoonful of onion jam, and a slice of brie on top. It was unreal. On little crackers it works too, and it’s perfect for a party table. Make the jam ahead, and put your bites together at the last minute so the bread stays crispy.

🎁 As a gift

In a pretty little clean jar, with a label where you write what it is and the date, it makes a holiday gift people love. Tell them to keep it in the fridge and eat it within the next few days. If you’re making some for several people, double the recipe in a bigger skillet, otherwise your onions will pile up and boil instead of caramelizing.

❄️ Storage

Onion jam keeps 3 to 5 days in the fridge, in a tightly closed jar. It freezes too: put it in small portions so you only take out what you need for a burger or a cheese board. Thaw it in the fridge the night before. Cold, warm or hot, it’s just as good, so you don’t even need to reheat it.

📅 Make-ahead prep

Onion jam is made to be prepped ahead: make it the day before and keep it in the fridge in its jar. On the day, just take it out a little before serving. What waits until the last minute is everything else: the bread that toasts, the brie you slice, the board you put together. That way, when people arrive, all you have to do is put it all on the table.

✅ What to serve with my onion jam recipe

A cheese board, a burger, a meat pie, a grilled cheese, charcuterie. Try it in my mini grilled cheese with brie or on my blue cheese burger. And if you love it, try my apple and onion bacon jam too, the version with bacon.