For the wonton cups: Put an oven rack in the center of the oven. Preheat the oven to 375 degrees F.
Using a pastry brush, brush each side of the wonton wrappers with canola oil. Gently press the wonton wrappers into the bottom and sides of a 12-count muffin pan. Bake until lightly golden, about 6 minutes. Remove the pan from the oven and let cool for 5 minutes. Gently lift the wonton cups out of the pan and cool completely, about 10 minutes.
For the filling: In a large, nonstick skillet, heat 3 tablespoons olive oil over medium-high heat. Drizzle the tilapia fillets with olive oil and season with salt and pepper, to taste. Arrange the fish in a single layer in the pan and cook until the flesh is flaky and cooked through, about 2 to 3 minutes on each side. Set aside to cool slightly.
For the dressing: In a medium bowl, whisk together the 3 tablespoons of olive oil and the lime juice. Season with salt, to taste. Add the avocado, mango, green onions, and arugula. Toss until all the ingredients are coated.
For the creme fraiche: In a small bowl, mix together the creme fraiche, wasabi powder and salt until smooth.
To assemble the tacos: Put the wonton cups on a platter and divide the avocado mixture into the cups. Top each with 3 to 4 pieces of fish. Spoon about 1 to 2 teaspoons of the creme fraiche mixture on top of the fish and serve.
Cook's Note: The wonton wrappers can burn very quickly in the oven so check them after 5 minutes.