Spray 2 1/2-quart souffle dish with nonstick cooking spray. In small saucepan, combine cornstarch and sugar. Add milk, 1/4 cup preserves and 3 tablespoons apricot nectar; mix well. Cook over medium heat until mixture boils and thickens, stirring constantly. Pour into large bowl; stir in vanilla. Cover surface with plastic wrap. Refrigerate about 1 hour or until completely cooled.
Heat oven to 425°F. In large bowl, beat egg whites and cream of tartar until stiff peaks form, about 2 to 3 minutes. Gently fold egg white mixture into cooled apricot mixture. Spoon into sprayed souffle dish. Place souffle dish in 13x9-inch pan; pour boiling water into pan around souffle dish to a depth of 1 inch.
Place in 425°F. oven. Immediately reduce heat to 350°F.; bake 25 minutes or until puffy, set and golden brown.
Meanwhile, in small saucepan, combine sauce ingredients; cook over medium heat until thoroughly heated. Serve souffle immediately with sauce.