How to Make It
Preheat the oven to 425°. In a small bowl, mix 1 tablespoon of the polenta with the cheese. Generously butter an 8-inch glass or ceramic baking dish and coat it with the polenta-cheese mixture.
In a medium saucepan, bring the milk to a simmer. Whisk in the remaining 1/2 cup of polenta and cook over moderate heat, stirring, until thickened, about 5 minutes. Remove from the heat. Whisk in the goat cheese, egg yolks, chives, 2 teaspoons of kosher salt and 1/2 teaspoon of pepper.
In a large bowl, beat the egg whites until stiff. Beat one-fourth of the egg whites into the polenta, then fold the polenta into the remaining egg whites with a large rubber spatula. Pour the mixture into the prepared baking dish and bake on the lowest rack of the oven for about 20 minutes, until the soufflé is golden, risen and only slightly jiggly in the center.
Meanwhile, in a medium bowl, whisk the olive oil with the lemon juice and season with salt and pepper. Add the arugula and radicchio and toss well. Transfer the salad to 4 plates. Spoon the soufflé alongside and serve.