Remove meat from lamb bone; cut into 1-inch cubes. Set bone aside.
Brown all sides of beef and lamb cubes in oil in a large Dutch oven over medium-high heat, stirring beef and lamb occasionally.
Add lamb bone, onion, and next 7 ingredients; bring to a boil. Cover, reduce heat, and simmer 30 minutes.
Remove lamb bone; add carrot, potato, and tarragon. Cover and simmer 30 minutes. Remove and discard bay leaves.
Combine flour and 1/4 cup water; stir until mixture is smooth. Slowly add flour mixture to stew, stirring constantly.
Cook over medium heat 3 minutes or until thickened and bubbly.
Cut puff pastry into shapes with a 5-inch shamrock cookie cutter. Place pastry shamrocks on an ungreased baking sheet.
Bake at 400° for 5 minutes or until lightly browned.
Spoon stew into individual bowls; top each with shamrock puff pastry.
Note: For the stout beer, we used Guinness.
* You can substitute 3 pounds trimmed lean boneless beef top sirloin steak, cut into 1-inch cubes, for lamb.
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