Follow these steps to create the perfect smoked salmon tarts:

1. Preheat your oven to 400°F (200°C). Lightly grease 24 mini-muffin cups to ensure easy removal of the tarts once baked.
2. Prepare the batter by combining the Bisquick mix, milk, Greek yogurt, soy sauce, and eggs in a bowl. Stir until the mixture is smooth and free of lumps.
3. Incorporate the flavor elements by folding in the shredded cheddar cheese, chopped smoked salmon, and sliced green onions. Ensure that these ingredients are evenly distributed throughout the batter.
4. Fill the muffin cups by spooning approximately 1 tablespoon of the mixture into each cup. This will ensure that the tarts are uniform in size and cook evenly.
5. Bake the tarts in the preheated oven for 15-20 minutes, or until they are golden brown and set. The tops should be slightly puffed, indicating that they are fully cooked.
6. Cool the tarts for about 5 minutes before gently removing them from the muffin cups. This cooling period allows the tarts to firm up slightly, making them easier to handle.
7. Store any leftovers in the refrigerator to maintain freshness. These tarts can be enjoyed cold or reheated in the oven for a few minutes before serving.