Red lentil, mushroom and spinach curry

From MSN's online edition of the Australian Women's Weekly (thanks, Google!) Modified slightly.

They say it's best made just before serving and not good for microwaving, but I disagree. It's better the second day.

1 cup dried red lentils
1 tablespoon vegetable oil
1 teaspoon cumin seeds
1 small onion, sliced thinly
1 clove garlic, crushed
1 tablespoon grated fresh ginger
1 small green chili pepper, sliced thinly
½ lb mushrooms, halved
1½ cups vegetable stock
½ cup water
½ teaspoon garam masala
1 10-oz or 1-lb package of frozen spinach, defrosted

YOGURT SAUCE
1 cup yogurt
1 clove garlic, crushed
½ teaspoon salt

Heat oil in wok or large frying pan. Add seeds, stir-fry until fragrant. Add onion, garlic, ginger and chili; stir-fry until onion is soft. Add mushrooms; stir-fry until browned lightly.

Add drained lentils, stock and water; bring to the boil. Reduce heat, simmer, uncovered, for about 5 minutes or until lentils are tender.

YOGURT SAUCE: Meanwhile, combine all ingredients in a small bowl.

Add garam masala and spinach to curry, stir until spinach is wilted; transfer to a serving dish.