Chili-Yogurt Mushrooms

I'm always craving Indian food... This is my first "out of a book" recipe, and it turned out really mouthwateringly good! I found this easy and the only extra thing I had to buy was the mushrooms. I already had everything else on hand.
Ingredients:
4 tbsp vegetable or peanut oil
2 large onions, chopped
4 large garlic cloves, crushed
3-4 juicy tomatoes, chopped
1 lb fresh mushrooms, thickly sliced
1tsp turmeric
1 tsp garam masala
1 tsp chili powder
1/4 cup water
1/2 cup plain yogurt
salt to taste
chopped cilantro for garnish
pinch of sugar
red pepper flakes (optional)

Directions:
1. Heat oil in a wok or large skillet and cook the onions, stirring frequently until golden (5-8 minutes). Add garlic and cook, stirring for an additional 2 minutes.
2. Add the tomatoes and their juice and stir well. Add turmeric, garam masala, and chili powder and cook, stirring for 3 minutes.
3. Add mushrooms, sugar and salt to taste. Adding salt with the mushrooms draws out their moisture. Cook covered for 8 minutes or until mushrooms have given off their liquid and are tender. If it seems a little dry, add the water.
4. Remove from heat, stir in yogurt viorously to prevent from curdling. Taste and adjust seasoning. I like it spicy, so I added red pepper flakes.
I served this as a side to my tandoori chicken and basmati rice with a sprig of cilantro. Oh so good!