Peel and chop the onion. Peel and dice the garlic and ginger.
Put a large saucepan on a medium heat and add the oil. When hot, add the onion, garlic and ginger. Cook, stirring often, for 3 minutes until softening.
Add the lentils and curry powder. Stir, then pour in the coconut milk and 400ml water. Add your chunkier frozen vegetables - the cauliflower and spinach chunks.
Turn down to a simmer and cook gently, stirring regularly, for about 20 minutes until the lentils are soft.
Add the peas - cook for another minute - then stir in the chopped coriander. Season with salt.
To make the yoghurt, chop the tomato and cucumber into 1cm pieces. Mix with the yoghurt and season with salt.
To serve, scoop the warm dahl into bowls and top with the cool yoghurt. Delicious!