In a bowl, combine the cooked rice, rice vinegar, sugar, and salt. Stir gently to mix, and let the rice cool to room temperature while you prepare the other ingredients.
- Julienne the cucumber and carrots, slice the avocado, and prepare your choice of protein (shrimp, crab, or tofu). If using tofu, you can pan-fry or bake it for extra flavor.
- Preheat the oven to 350°F (175°C). Lightly grease a muffin tin or line it with parchment paper. Spoon a small amount of rice into each muffin cup, pressing it down gently to form a base. Top with cucumber, carrots, avocado, and protein. Sprinkle sesame seeds and add strips of nori if desired.
- Bake for 10-12 minutes or until the cups are warm and slightly crispy around the edges. Alternatively, serve raw if you prefer.
- To prepare the soy-ginger sauce, whisk together soy sauce, rice vinegar, honey or maple syrup, sesame oil, ginger, and water. Adjust the sweetness and saltiness to taste.
- Once the cups are ready, remove from the oven and let them cool slightly. Drizzle with the soy-ginger sauce and garnish with additional sesame seeds, nori strips, or fresh cilantro.
- Serve immediately and enjoy!