Combine stock, butter and 2 teaspoons salt in heavy medium saucepan and heat until butter melts and liquid just comes to boil. Remove from heat. Whisk in flour all at once. Set pan over low heat and stir until dough forms ball and film forms on bottom of pan, about 5 minutes. Remove from heat. Cool 7 minutes. Beat in eggs 1 at a time. Add egg whites and beat until shiny and smooth, about 5 minutes. Cover dough and let stand at room temperature until ready to use. Position rack in center of oven and preheat to 350°F. Generously butter 12-cup loaf pan. Coarsely chop veal in processor using 4 to 5 on/off turns. Add chicken and coarsely chop using 4 to 5 on/off turns. Add remaining salt, leeks, thyme, nutmeg and cayenne and blend 1 minute. With machine running, add cream through feed tube in thin stream, stopping to scrape down sides of bowl. Add meat mixture to dough and blend well. Spoon mixture into prepared pan. Smooth top using back of metal spoon dipped in cold water. Tap pan on surface several times to eliminate air bubbles. Wrap pan tightly in buttered foil. Set in shallow roasting pan. Add enough boiling water to come 3/4 up sides of loaf pan. Bake until tester inserted in center comes out almost clean or until instant-reading thermometer inserted in center registers 180°F to 190°F, about 2 hours. Remove from water bath. Carefully peel off foil. Cool loaf to room temperature. Wrap well. Refrigerate at least 12 hours. To unmold, run thin sharp knife around edge of pan. Set bottom in hot water for 2 minutes. Invert loaf onto work surface. Turn upright and cut into thin slices. Spoon some of sauce onto platter. Alternate loaf and tomato slices on platter. Garnish with arugula leaves. Pass remaining sauce separately. Arugula Sauce This can be prepared up to four hours ahead. Do not refrigerate any longer, or sauce may become bitter. Makes about 3 cups 3 quarts water Salt 4 firmly packed cups trimmed arugula (about 4 bunches) 2 eggs, room temperature 1 egg yolk, room temperature 1/3 cup white wine vinegar 1 tablespoon Dijon mustard 1 teaspoon salt 1 cup olive oil 1 cup corn oil Bring water to boil in heavy large saucepan. Stir in salt. Remove pan from heat. Stir in arugula. Drain immediately. Plunge into large bowl of ice water. Let cool completely. Drain well; squeeze dry. Coarsely chop arugula. Transfer to processor. Add eggs, yolk, vinegar, mustard and salt and blend 1 minute, stopping to scrape down sides of bowl. With machine running, add oils through feed tube in thin stream. Adjust seasoning. Transfer to bowl. Cover and refrigerate up to 4 hours. Serve immediately. appet 59