Preheat the oven to 450°. In large skillet melt butter over medium heat and sauté leeks until softened but not browned, about 4 minutes. Place pizza crust on a nonstick baking sheet. Layer peppers around pizza, leaving about a 3/4-inch border. Add leeks, chicken and top with cheese. Sprinkle with dried basil and bake 15 minutes or until crust is golden and cheese melted. Add fresh basil leaves if desired.