Toast the bread: Lightly toast 2–3 slices until golden. This keeps the sandwich sturdy and adds crunch.
Mix the spread: In a small bowl, combine Greek yogurt, Dijon, lemon juice, olive oil (if using), salt, pepper, and a pinch of smoked paprika or garlic powder.
Season the chicken: Slice the cooked chicken breast thinly. Sprinkle with a little salt and pepper for extra flavor.
Prep the veggies: Slice the tomato and avocado.
Rinse and pat dry the lettuce. Thinly slice red onion if using.
Build the base: Spread the yogurt-Dijon sauce on one slice of toast. Add lettuce and tomato.
Season the tomato with a tiny pinch of salt.
Add the chicken: Layer on the sliced chicken. If using turkey bacon, add it now for crunch and a smoky note.
Creamy layer: Add avocado slices. Press gently so they adhere to the chicken.
Top and slice: Spread more sauce on the top slice of bread.
Close the sandwich. If using a third slice (classic club style), place it in the middle with a light smear of sauce on both sides. Cut in half or into triangles.
Serve: Enjoy right away with a side of fruit, sliced cucumbers, or a small green salad.