Whisk together first 6 ingredients; pour into a large heavy-duty zip-top plastic bag, and add mahi mahi. Seal and chill 8 hours, turning occasionally.
Combine sesame seeds and flour in a shallow dish. Remove fish from marinade; pat dry with paper towels. Coat fish on all sides with sesame seed mixture.
Heat sesame and peanut oils in a large nonstick skillet over medium-low heat. Add fish; cook 2 to 3 minutes or until golden. Turn over, reduce heat to low, and cook 2 to 3 minutes until fish flakes easily with a fork. Serve over Cucumber-Watercress Salad.
Great flavor & light! Used frozen mahi mahi fillets that I thawed, omitted tahini, & substituted baby arugula for the watercress. Only marinated the fish 1 hr, and cooked longer than recipe said (about 6-8 minutes for each side). Also served with oven-roasted dill potatoes.
This recipe was served for a dinner party, for 4 people. For appetizers, we had served sushi (california & spicy tuna roll), with beer or oolong tea. We were able to eat dessert about 45min-1hr later without feeling overly full. (Made Chocolate-Orange cake...<http://allrecipes.com//Recipe/zucchini-chocolate-orange-cake/Detail.aspx>).