Start the soup: Set a large soup pot on the stove over medium-high heat.

Add the olive oil to the pot and heat it until it looks loose and shiny, about 30 seconds.

Add the chopped onion and sliced celery to the pot. Cook, stirring often, until they start to soften, 3 to 4 minutes.

Add the cauliflower florets to the pot. Cook, stirring every minute or so, until a few edges pick up light brown spots, 4 to 5 minutes.

Add the sliced garlic and harissa paste to the pot. Stir for 30 seconds, just until the garlic smells fragrant and the harissa coats the vegetables.

Add the drained chickpeas to the pot. Stir them through the vegetables for about 1 minute.

Pour the vegetable broth into the pot. Add the 1 teaspoon of kosher salt and stir well.

Build the broth: Raise the heat and bring the broth to a boil.

Lower the heat to a steady simmer. Cook until the cauliflower is tender when pierced with a fork, 8 to 10 minutes.

Taste the broth and add more salt if needed. The broth should taste well seasoned now, because the noodles will absorb some of it.

Cook the noodles: Add the rice noodles to the simmering pot. If they are very long, break them in half first so they fit into the broth more easily.

Press the noodles down into the broth with a spoon. Cook at a gentle simmer, stirring once or twice, until the noodles are tender and no longer chalky in the center, 3 to 4 minutes.