Heat the olive oil in a large stock pot and over medium heat. Add in the onions, carrots, celery and garlic with a big pinch of salt and pepper. Cook, stirring often, until the vegetables softed, about 5 to 6 minutes.

Stir in the broccoli and cook for another 5 minutes. Add in the parmesan rind, the shredded chicken and the chicken stock. Bring the mixture to a boil, then reduce it to a simmer.

Combine the milk and flour in a shaker cup (or even in a measuring cup and use a whisk) for 30 seconds, until the flour is fully incorporated. Stream the slurry into the soup, stirring the entire time.

Let the soup simmer uncovered for 10 to 15 minutes, stirring often - it will thicken and cook down a bit.

Taste and season with more salt and pepper if needed. Spritz in the lemon juice and stir.

Serve immediately!