Heat oil in a saucepan over a medium heat. Cook onion for 8 to 10 minutes or until tender. Add garlic and curry powder. Cook for 2 minutes or until fragrant.
Add lentils, ginger, coconut milk and stock. Bring to the boil. Reduce heat to low. Simmer, partially covered, for 30 minutes or until lentils have softened. Cook, uncovered, stirring occasionally, for 20 to 30 minutes or until thickened. Remove from heat. Stir in spinach. Serve warm with coriander.