Heat large stock pot.
Dice bread cubes for croutons and put in a 400* oven or low broil. WATCH so they don’t burn!
Drizzle in olive oil to hot pot and sauté celery, then add garlic a bit later.
When garlic is golden, add potato and stock, bring to boil, then reduce heat and simmer for 10 minutes or until potato is tender.
Meanwhile, sauté mushrooms in a pan with butter. Once brown and bubbly, set aside.
Add greens to soup and cook until wilted.
Add mixture to blender. Blend away.
Pour into two bowls.
Garnish with mushrooms and croutons.