Prep the broccoli by removing all the florets from the crowns. Take a small portion of those florets and chop them into small pieces until you have about 1½ cups; set these aside for the crispy topping. Leave the remaining florets and the short crown stems in large pieces to simmer in the soup.

Heat the oven to 425°. Arrange the bacon on a baking sheet and roast until the fat has rendered and the slices are crisp, 7 to 10 minutes. Transfer the bacon to a paper towel–lined plate and crumble or chop into small bits for topping.

On the same baking sheet, toss the finely chopped broccoli florets in the rendered bacon fat, season generously with salt, and roast until deeply caramelized and crisp, 7 to 10 minutes. Set aside.

In a large pot, warm 1 tablespoon avocado oil over medium heat. Add the onion and cook until soft and translucent.

Stir in the roasted garlic, broccoli stems, parsnips, and 1 teaspoon salt. Pour in 6 cups of the stock, reserving the remaining 2 cups to thin the soup later if needed.

Cover and bring to a simmer. Uncover and cook until the stems and parsnips are tender, about 15 minutes.

Add the remaining broccoli florets and simmer until bright green and fork-tender, about 5 minutes more. Stir in the nutritional yeast and remove from the heat.

Blend with an immersion blender until smooth, or work in batches with a countertop blender. Return the soup to the pot and season to taste. If needed, thin with additional stock to your preferred consistency.

Serve topped with the crispy bacon and roasted broccoli florets.