In a large saucepan, bring water to a boil. Whisk in polenta and 1 teaspoon salt.
Turn heat to low. Polenta should be barely barely simmering. Stir occasionally, so polenta doesn't stick to bottom.
While polenta is cooking, heat olive oil in a medium saucepan to medium high. Add leeks and cook for 4 minutes, until translucent. Add tomatoes, and cook for 10 minutes on medium, until they are bursting. Add kale leaves, stirring to coat with other ingredients.
Cook on low for 5-8 minutes, until kale is wilted. Stir a 1/2 teaspoon salt and black pepper into mixture.
After 35 minutes, polenta should be thick and creamy. Removed from heat, and add yogurt and butter. Whisk until completely smooth.
Spoon polenta into bowls and top with tomatoes and kale mixture, then add extra dollop of yogurt and drizzle of olive oil. Serve.