Sauté the vegetables in the clarified butter and olive oil over medium heat. Add the onion and celery, and sauté for about 5 minutes until tender and golden brown. Add the garlic and cook for 1 minute more.
Add the broccoli, along with the rosemary and oregano. Cook for about 5 minutes, stirring occasionally, to soften the broccoli.
Sprinkle the oat flour over the vegetables and mix well.
Pour the 4 cups of oat milk into the saucepan, stirring well to avoid lumps. Bring the mixture to a gentle boil, then reduce heat to low.
Simmer for 10-15 minutes, until the broccoli is very tender and the soup has thickened slightly.
Process the soup Transfer the mixture to a blender or use a hand blender to process the soup to a completely smooth and creamy consistency. Make sure there are no lumps.
Season with salt and pepper to taste. If you prefer a thicker texture, you can add a little more oat flour.
Serve the broccoli cream piping hot. You can garnish with a drizzle of olive oil or a sprinkling of fresh rosemary.