• Let’s roll up our sleeves and dive into making this masterpiece.

Step 1: Caramelizing the Onions

• Start by melting the butter in a large pot over medium heat. Once melted, add the finely diced onions. Stir them consistently, allowing them to soften and caramelize. The process usually takes about 20-30 minutes. The key here is patience; you want them to turn a golden brown. The silence in your kitchen, coupled with that sweet aroma, sets the perfect mood!

Step 2: Adding the Flour

• Once the onions reach a sweet golden color, sprinkle in the flour. This will help thicken the soup. Stir well to coat the onions, letting the flour cook for another minute or two.

Step 3: Incorporating the Broths

• Carefully pour in the beef broth and chicken broth. The mixture should bubble slightly as you combine it. This is where the magic begins! Then, add the beef bouillon concentrate, thyme, and sea salt. Stir everything together and let it simmer on low heat for 15-20 minutes. You’ll smell those captivating flavors combine beautifully.

Step 4: Adding Final Touches

• After simmering, add balsamic vinegar and smoked paprika. Stir until everything is combined. The balsamic adds a hint of depth, while the smoked paprika introduces a subtle warmth.

Step 5: Serving with Croutons and Cheese

• Ladle the soup into oven-safe bowls. Top generously with toasted croutons and a sprinkle of both Gruyère and Asiago cheese. We want that gooey, bubbling goodness! Place them under the broiler for about 3-5 minutes until the cheese is melted and slightly browned. Watch closely; you don’t want to miss this glorious moment.