Decide grilled or crispy: For grilled chicken, butterfly each breast to about 1/2" thickness or pound between plastic wrap to even thickness. For crispy chicken, leave breasts whole or cut in half for sandwich-sized fillets.

Prepare a basic seasoning mix: in a small bowl combine 1 tsp garlic powder, 1 tsp smoked paprika, 1 tsp salt and 1/2 tsp black pepper. Rub 1 tbs olive oil over the chicken and evenly coat with the seasoning mix. For grilled chicken, set aside 10 minutes to come to room temperature (or marinate up to 2 hours).

If making crispy chicken: pour 1 cup buttermilk into a shallow dish and add a pinch of salt. In another dish whisk together 1 cup flour, 1/4 cup cornstarch and 1/4 tsp cayenne (optional). Dip each chicken piece into buttermilk, then dredge thoroughly in the flour mixture, pressing to adhere. Let rest on a rack 10 minutes while you heat oil.

For grilled chicken: heat a grill pan or outdoor grill to medium-high (about 400°F / 200°C). Brush grates or pan with 1 tbs olive oil. Grill the breasts 4–6 minutes per side until internal temperature reaches 165°F (74°C) and edges are nicely charred. Transfer to a plate and rest 5 minutes; then slice to sandwich size.

For crispy chicken: heat vegetable oil in a deep skillet or pot to 350°F (175°C). Fry the dredged chicken 4–6 minutes per side (depending on thickness) until golden brown and internal temperature reaches 165°F (74°C). Transfer to a wire rack over a sheet pan to drain and rest 5 minutes.

For the sandwich and toppings

Slice the tomato into 1/4" rounds. Lightly season the tomato slices with 1/4 tsp salt and 1/8 tsp black pepper; set aside so juices develop while you finish the chicken.

Split buns and spread 1 tbs butter on cut faces. Toast buttered buns in a skillet over medium heat or under a broiler until golden, about 1–2 minutes per side. Remove and keep warm.

Assemble sandwiches: spread 2 tbs mayonnaise on the bottom bun. Place 1–2 lettuce leaves, then a grilled or crispy chicken breast (whole or halved), top with 2–3 tomato slices and additional mayonnaise on the top bun if desired. Close sandwich and press gently. Cut in half if desired and serve immediately.

For the fries

If using frozen fries: bake or fry according to package directions. Season with 1 tsp salt immediately after cooking and toss to coat.

If using fresh cut potatoes: preheat oven to 220°C (425°F). Toss 400 g cut potatoes with 2 tbs vegetable oil and spread in a single layer on a rimmed baking sheet. Roast 25–30 minutes, turning halfway, until golden and crisp. Sprinkle with 1 tsp salt and serve alongside sandwiches.