Melt 2 tablespoons butter in a skillet; add potato and next 4 ingredients. Sauté 20 minutes or until tender. Stir in ham and next 3 ingredients; set aside.
Whisk together 1/4 cup butter, flour, and 1/4 teaspoon salt in a heavy saucepan over low heat until smooth; cook, whisking constantly, 3 minutes or until bubbly. Gradually add milk; cook over medium heat, whisking constantly, until thickened and bubbly. Remove from heat.
Beat egg yolks until thick and pale. Gradually stir about one-fourth of milk mixture into yolks; add to remaining milk mixture, stirring constantly. Cook over medium-low heat, stirring constantly, 2 minutes or until slightly thickened. Pour batter into a large bowl, and let cool.
Line a 15- x 10-inch jellyroll pan with parchment paper; lightly grease paper with vegetable cooking spray.
Beat egg whites at high speed with an electric mixer until stiff peaks form; fold into batter, and spread evenly in prepared pan.
Bake at 400° for 15 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 5 minutes.
Turn soufflé out onto a cloth towel, and remove paper. Return paper to pan. Top soufflé evenly with vegetable mixture, and sprinkle with cheese. Beginning at a long side, roll up, jellyroll fashion; place roll, seam side down, in pan.
Bake at 350° for 10 minutes or until thoroughly heated and cheese melts. Slice with a serrated knife, and serve with Salsa. Garnish, if desired.
Four Cheese: Combine 1/2 cup grated Parmesan cheese, 1/2 cup (2 ounces) shredded Monterey Jack cheese, and 1/2 cup (2 ounces) shredded mozzarella cheese, and sprinkle over soufflé; top with 4 (1-ounce) slices provolone cheese. Roll and proceed as directed.
Spinach and Feta: Sprinkle soufflé with 1 (10-ounce) package frozen chopped spinach, thawed and drained well; 1 (4-ounce) package crumbled feta cheese; and 1/2 cup coarsely chopped pitted kalamata olives. Toll and proceed as directed.
Shrimp and Dill: Peel 1 pound medium-size fresh shrimp, and devein, if desired. Sauté in 1 tablespoon melted butter until pink; drain and coarsely chop. Stir together shrimp; 1 (8-ounce) package cream cheese, softened; 1/2 teaspoon salt; and 1/2 teaspoon freshly ground pepper until blended. Spread over soufflé. Top with 4 (1-ounce) slices provolone cheese; roll and proceed as directed.