Grilled Tuna Kebabs with Wasabi Sauce

Name: Grilled Tuna Kebabs with Wasabi Sauce
Ingredients: 1 1/2 lb sashimi grade tuna; 16 large shiitaki mushrooms; 2 large sweet red peppers; 1 large red onion; 8 skewers if using bamboo soak in water; 1 1/2 c sherry soy marinade; 1 to 2 tsp wasabi paste; 1/2 c oil canols, vegetable or vpeanut; 1/2 c dry sherry; 1/4 c soy sauce, low sodium; 2 Tbsp sesame oil; 2 Tbsp peeled chopped ginger root; 2 Tbsp minced garlic; 1/4 c chopped cilantro; 3 scallions sliced; 3 Tbsp rice wine vinegar; 2 Tbsp ground cumin; 1 Tbsp achiote paste optional