Saute onion with curry powder in butter until crisp-tender. Blend in cornstarch. Add 2 cups of the milk and cook, stirring constantly until mixture boils, 1 to 2 minutes. Pour into a blender container and let cool a few minutes. Blend until smooth and remove to saucepan.
Add boiling water to broccoli and cook until just tender. Put broccoli, one-half at a time, in blender container (no need to clean it out from the onion mixture) and blend with the remaining 1 cup of milk until smooth. Add the blended broccoli to the onion mixture in saucepan. Add oregano, and salt and pepper to taste. ( I use 1 teaspoon salt and ¼ teaspoon pepper) Heat until very hot over medium low heat, but do not boil. Ladle soup into bowls and place a lemon slice on top of each bowl of soup.
(Note: If you really love lemon (I do!) I even add a slice of lemon in the bottom of bowl before adding soup and then another on top. The bottom lemon is not necessary, but the top one is! It adds a delicate touch and a great flavor. Adding both lemons is for lemon-lovers only!)
Makes about 6 cups.
Recipe by The Culinary Cellar at https://theculinarycellar.com/revisiting-bakery-lane-soup-bowl/