Peel, core, and chop apples; set aside.
Chop onion. Heat oil in a sauce pan over medium; add onion and sauté until translucent without allowing to brown.
Add curry powder and cornstarch; stir and cook for 2 minutes. Add apples and broth. Bring to a boil, stirring constantly. Continue to stir, allowing soup to thicken.
Stir in raisins, 2 tablespoon of lemon zest, 2 tablespoon of fresh lemon juice, salt, and pepper. Reduce heat to a simmer and cook for 15-20 minutes, continuing to stir occasionally.
Remove from heat and allow soup to cool slightly. Add to blender and blend until smooth, working in batches if necessary. Pour into saucepan.
In a small bowl, whisk together the egg yolks and cream. Add to soup and heat through without boiling.
Serve hot with crackers on the side.