Beat yogurt and eggs together; add water; stir in flour. Mix together well with egg beater. Add peppers. Cook over medium heat, stirring occasionally until mixture comes to a boil. Meanwhile cook each vegetable separately. Celery -- cook 10 minutes; swiss chard -- cook 2 minutes until soft; spinach -- add salt to taste and cover with boiling water, strain, repeat. Add yogurt, celery, swiss chard, and spinach (in that order). Cook for 10-15 minutes until mixture comes to a boil. Remove from heat and stir for 5 minutes. Season with coriander. How many people this serves depends on how well they like yogurt!