Mix 1 tablespoon hoisin sauce and soy sauce together in a bowl. Add the mushrooms and stir to coat.
Heat wok over high heat until hot. Add oil and mushrooms and stir-fry for 2-3 minutes until tender. Add duck breast and stir-fry for 2 minutes until heated through.
Spread the warmed pancakes with remaining hoisin sauce. Top with mushroom and duck mixture, cucumbers and green onions. Roll up and serve with extra hoisin sauce if desired.