Preheat the oven to 425°F while you are chopping the vegetables.
Add the chopped broccoli, 1 tablespoon of olive oil, and 1 teaspoon of salt to a rimmed roasting pan. Toss to coat and roast for 20 minutes, stirring once about halfway through. The broccoli should be cooked through and lightly browned in places.
2 heads broccoli, florets cut and stems trimmed and chopped, 2 tablespoons olive oil, divided, 2 teaspoons salt, divided
At the same time, toast the almonds in a small pan for 5 to 10 minutes until they start to smell nutty.
1 cup blanched slivered or whole almonds
While the broccoli and nuts are in the oven, add the remaining tablespoon of olive oil to a large soup pot and turn the heat up to medium.
2 tablespoons olive oil, divided
When the oil is hot, add the potato, carrot, celery, onion, and garlic and cook, stirring occasionally, until the vegetables are starting to brown.
1 Yukon gold potato, scrubbed and chopped, 1 carrot, peeled and chopped, 1 stalk celery, chopped, ½ large onion or 1 medium onion, chopped, 3 cloves garlic, smashed
Add water to cover and then stir in the remaining one teaspoon of salt and the ground black pepper, red pepper flakes, and parsley. Bring the pot to a boil and then reduce the heat to medium-low, cover the pot, and let the vegetables simmer for 20 minutes, stirring occasionally.
2 teaspoons salt, divided, ¼ teaspoon ground black pepper, ¼ teaspoon red pepper flakes, 3 sprigs of parsley
When the broccoli and almonds are done, reserve a few broccoli florets and almonds for garnish.
Working in batches, use your blender or food processor to purée the soup, broccoli, and almonds together to a thick consistency.
Turn the heat back to low, add the cider vinegar, and adjust the salt and pepper as needed.
1 tablespoon apple cider vinegar
Garnish with the reserved broccoli florets and almonds. Serve hot.