Make Hollandaise sauce according to directions on package. In a large skillet over medium heat, cook and stri ham and onions in butter until onions are tender. In large bowl, whisk 6 eggs and milk. Add egg mixture to the pan; cook and stir until set. Remove from heat; stir in 1/3 c. hollandaise sauce (or more to taste). Set aside.

On a lightly foured surface, unfold puff pastry. Roll each sheet into a 12×9 in. rectangle; cut each in half widthwise. Place 1 c. egg mixture on half of each rectangle; sprinkle with cheese.

Beat water and remaining egg; brush over pastry edges. Bring an opposite corner of pastry over the egg mixture; pinch seams to seal. With a small sharp knife, cut several slits in the top. Transfer to a greased baking sheet; brush with remaining egg mixture. Bake at 400* for 18-22 minutes, until golden brown. Serve with remaining hollandaise sauce. Sprinkle with tarragon.