Gather all your ingredients and prepare for the cooking process.

Heat a large pot over medium heat. Pour in some olive oil and add your chopped onions and minced garlic.

Sauté the onions and garlic until they become soft and translucent, stirring occasionally to prevent burning.

Add the diced carrots and celery to the pot. Continue to sauté until these vegetables start to soften, about 5 minutes.

Sprinkle the flour over the vegetables, stirring constantly to coat them evenly. This will help thicken the soup later. Add your chopped herbs at this stage to begin infusing the soup with flavor.

Slowly pour in the milk while continuously stirring to incorporate the flour and form a smooth mixture without lumps.

Add the sliced mushrooms to the pot. Stir well to combine with the other ingredients.

Season the soup with salt and pepper according to your taste. Adjust the seasonings to ensure a balanced flavor profile.

Pour in the vegetable broth and bring the mixture to a simmer. Let the soup cook, uncovered, for about 20 minutes, or until all the vegetables are tender and the soup has thickened to your liking.

Once the soup is ready, give it a final taste and adjust any seasonings if necessary. Serve hot, garnished with additional fresh herbs or a sprinkle of grated cheese if desired.