Lightly toast two slices of bread until golden and crisp.
In a small bowl, combine 0.25 cup mayonnaise, 1 teaspoon Dijon mustard, 0.25 teaspoon black pepper, and 0.125 teaspoon garlic powder (optional). Stir until smooth.
Spread the creamy mayonnaise mixture evenly on both slices of toasted bread.
On one slice, layer two slices of sharp cheddar cheese (optional).
Pile 0.5 cup thinly sliced dill pickles on top of the cheese layer, arranging them evenly.
Place the second slice of bread on top, press gently, and slice the sandwich in half. Serve immediately.