Thermomix French Onion Soup

Name: Thermomix French Onion Soup
Prep time: 15 min
Cook time: 50 min
Total time: 65 min
Ingredients: 100 g gruyere cheese; 800 g brown or yellow onions (halved); 100 g butter; salt and pepper (to taste); 8 g plain flour; 800 g beef or chicken stock liquid; 2 bay leaves (optional); 1 tbs fresh thyme (optional); 1 baguette (sliced into 12-16 pieces)

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A classic, flavoursome Thermomix French Onion Soup topped with cheesy baguette slices. The perfect winter warmer!

An overhead shot of slices of cheesy baguette on top of a French onion soup.

There's nothing more comforting than a bowl of warm French onion soup on a cold wintery day.

You won't be able to resist the slightly sweet soup topped with plenty of slices of crunchy grilled baguette with melted cheese on top.

Just like our minestrone soup, chicken noodle soup and pumpkin soup recipes, the Thermomix takes all the fuss out of prepping and cooking restaurant quality soup recipes at home.

Why You're Going To Love This Recipe

You won't be able to resist our classic Thermomix French onion soup recipe!

Cafe-Style At Home - in the past I would only eat French onion soup if I was out at a cafe or restaurant... but once you've made it in your Thermomix (and realise how simple it is!), you'll be enjoying it at home on high rotation!
Cheesy Toastie Melts - ohhh the crunchy baguette slices with melted gruyere cheese and AMAZING!!!!!!! They really take this soup to the next level!
Suitable For Any Thermomix Model - you can make our soup using any of the Thermomix models... from the TM31 through to the TM6.
Freezer-Friendly - the onion soup (without the baguette slices) can be frozen, however, you'll need to make fresh cheesy toastie melts when you reheat the soup (see my tips below).

Melted cheese baguettes on top of onion soup.

What You Need

Making homemade Thermomix French Onion Soup is so easy (and almost entirely hands-off too!).

Please scroll to the recipe card at the bottom of the post for ingredient quantities and the full detailed method.

The ingredients for Thermomix French Onion Soup.

Gruyere Cheese - this is the cheese traditionally used for melting over the baguettes in French onion soup. Alternatively, you can substitute it for cheddar or tasty cheese if you prefer.
Onions - yellow onions or brown onions can be used in this recipe.
Butter - either salted or unsalted butter can be used.
Plain Flour - also known as all-purpose flour.
Liquid Stock - you can use beef or chicken stock liquid - the choice is yours! Chicken stock tends to give the soup a lighter flavour, whereas beef stock tends to be richer in flavour.
Bay Leaves & Thyme - optional, but recommended.
Baguette - thinly slice a baguette or French stick.

Step By Step Instructions

Let's get started making Thermomix French onion soup!

Please scroll to the recipe card at the bottom of the post for ingredient quantities and the full detailed method.

Step 1 - Grate The Cheese

Place the cheese into the Thermomix bowl and mix until finely grated.

Set aside in a seperate bowl.

Wash and dry the Thermomix bowl.

Step 2 - Chop & Saute The Onions and Butter

Place the butter and the halved onions into the Thermomix bowl.

Season with salt and pepper and then mix until chopped.

Scrape down the sides of the bowl and then saute for 15 minutes.

Note: Remove the MC and place the splatter guard or rice basket on top of the lid before cooking.

Chopped onions and butter in a stainless jug.

Use the spatula to stir the onions (ensuring that you move and lift any onions from the base of the bowl - to stop them from sticking).

Cook for a further 15 minutes.

Step 3 - Cook The Soup

Pour in the stock liquid and add the plain flour. Mix with the MC ON for 15 seconds to combine.

Remove the MC, add the bay leaves and thyme (if using) and then cook the soup for 20 minutes.

Yellow liquid and flour in a Thermomix bowl.

Remove and discard the bay leaves and thyme.

Divide the soup into bowls and top with the cheesy melted baguette slices (see tips below).

Expert Tips

It's important to scrape the onions from the base of the Thermomix bowl in between the cooking times. This helps to ensure that they don't stick to the base.
While the soup is cooking, cook the cheese toastie slices - place thinly sliced baguette pieces onto a flat baking tray. Sprinkle the reserved gruyere cheese over the top and grill in the oven until golden and melted. Place on top of the bowls of soup when serving.
Do NOT exceed the MAX line - at no stage should you exceed the MAX line in the Thermomix machine. This is particularly important with the TM31 as the bowl is smaller than the TM5 and TM6. If you are close to the MAX line, use less chicken stock liquid.
MC OFF - for safety reasons, it's important to remove the measuring cup (MC) when cooking at very high temperatures. To avoid splatters, place the splatter guard or simmering basket over the top of the lid instead.
Store in an airtight container in the fridge for up to 3 days.
Reheat frozen soup in a pot on the stovetop or in the microwave.
Reheat defrosted soup in the microwave, on the stovetop or in the Thermomix.
The onion soup (without the baguette slices) can be frozen for up to 3 months, however, you'll need to make fresh cheesy toastie melts when you reheat the soup (see my tips below).

FAQs

Why do I have to use the REVERSE function in some steps?

The REVERSE function is used when we want to stir rather than chop. As the onions have already been chopped, we simply want to stir them while they saute and cook.

Why do I have to remove the MC?

The MC (measuring cup) needs to be removed when cooking at high temperatures. This is for safety reasons as the steam in the Thermomix builds up and cannot escape. Place the splatter guard (or the simmering basket) over the hole in the MC lid instead - this stops splatters while allowing the steam to escape.