Heat oven to 400ºF. Grease 15x10x1-inch pan. In 2 1/2-quart saucepan, heat butter and water to rolling boil. Stir in flour; reduce heat to low. Stir vigorously about 1 minute or until mixture forms a ball; remove from heat. Beat in eggs all at once; continue beating until smooth. Spread dough in pan.
Bake about 30 minutes or until golden brown. Cool completely, about 30 minutes. (Crust will be puffy and uneven.)
In large bowl, beat cream cheese and 1/4 cup of the milk with electric mixer on low speed until smooth. Add remaining milk and the pudding mix (dry). Beat about 2 minutes or until smooth and slightly thickened; immediately spread over crust. Spread with whipped topping.
Refrigerate uncovered at least 1 hour but no longer than 24 hours. Just before serving, drizzle with chocolate syrup and sprinkle with nuts. For servings, cut into 6 rows by 4 rows. Store in refrigerator.