Two hours ahead of time, place the yogurt in a strainer lined with a coffee filter and set over a bowl. Place in the refrigerator and let yogurt drain for two hours. At serving time, cut large tomatoes into chunks or wedges; cut small tomatoes in half or quarters. Place all tomatoes in large bowl. Place vinegar in small bowl and whisk in sugar, salt, pepper and drained yogurt. Drizzle in olive oil while whisking so as to form an emulsion. Pour over tomatoes, add chives, and stir. Serve over pieces of toasted country bread.
TOASTED COUNTRY BREAD
Preheat oven to 350 degrees. Brush bread slices lightly with olive oil on both sides. Place on rack placed on a cookie sheet and place in oven. Toast for 1015 minutes, or until just beginning to brown. Spoon tomato salad on top and serve.