Spicy Tuna and Avocado Cucumber Sushi Bites

Name: Spicy Tuna and Avocado Cucumber Sushi Bites
Prep time: 20 min
Total time: 20 min
Cuisine: Asian, American, Japanese
Ingredients: 1/2 pound ahi tuna (sushi-grade), finely diced; 1 tablespoon soy sauce; 1 teaspoon sriracha (or to taste); 2 teaspoons mirin (optional); 2 tablespoons green onions, finely sliced; 1/2 teaspoon toasted sesame oil; 2 teaspoons black sesame seeds, toasted (optional); 1 cucumber, sliced thinly; 1 avocado, thinly sliced