Heat the oil in a large pot over medium heat. Add the onion, garlic, and ginger, and stir-fry for a few minutes until fragrant.

Stir in the red curry paste, turmeric, salt, and sugar. Continue to stir-fry for another few minutes, allowing the spices to bloom.

Add the baby Yukon potatoes and coconut milk to the pot. Bring to a simmer and cook until the potatoes are tender when pierced with a fork.

Allow the soup to cool slightly, then carefully transfer it to a blender. Puree until the soup is smooth and silky, thick enough to coat the back of a spoon.