Bring a large pot to a medium heat. Add olive oil and then the cumin seeds, turmeric, mustard seeds and red chilli flakes. Sauté, stirring, until fragrant.
Add the ginger and garlic to the pan and stir, sautéing until fragrant.
Next, add the carrot, onion and celery to the pan and sauté until the onion is translucent .
Add the pumpkin, tomato paste and vegetable stock. Stir until well combined. Add the lentils and stir through.
Bring the pot to the boil and then reduce to a simmer, simmering until the pumpkin and lentils are soft and tender.
Remove from the heat and use an immersion blender to carefully blend the soup until smooth. Alternatively, cool the soup to room temperature before transferring to a blender to blend until smooth.
Season to taste with salt and pepper.
Serve warm topped with natural yogurt and chili flakes if desired.
Notes
Storage
Store in the soup pot, with lid on, or in an airtight container with the lid on, in the fridge for up to 4 days. To freeze, divide between individual serving sized freezer safe containers. Freeze for up to 6 months.