Heat vegetable oil in a large pot over medium heat. Sauté diced onion for 5 minutes until translucent.
Stir in minced garlic and grated ginger, cooking for another minute until aromatic.
Add red curry paste and cook for 2 minutes to bloom the spices.
Pour in coconut milk and vegetable broth, stirring to combine. Bring to a gentle simmer.
Add mixed vegetables and soy sauce, cooking for 5-7 minutes until tender.
In a medium bowl, combine flour, baking powder, and salt. Gradually stir in milk to form a soft dough.
Drop spoonfuls of dumpling dough into the simmering soup, spacing them out.
Cover the pot and steam dumplings for 10 minutes without lifting the lid.
Stir in lime juice and season with salt and pepper to taste before serving.