Prepare the Eggs
Crack the eggs into a small bowl. Add a pinch of salt, pepper, and milk or cream, if using. Whisk until the yolks and whites are fully combined.
Cook the Eggs
Heat the butter or oil in a non-stick skillet over medium-low heat. Pour in the egg mixture and let it sit for a few seconds before gently stirring. Cook the eggs slowly, stirring often, until they are just set and creamy. Remove from heat.
Assemble the Sandwich
Toast the bread or bun to your desired level of crispiness. Place a slice of cheese on one piece of the toast. Spoon the scrambled eggs over the cheese, then add any additional toppings, such as avocado slices, bacon, or spinach.
Finish and Serve
Place the other slice of bread on top, gently pressing to secure the sandwich. Serve warm, and enjoy!