Preparing The Chicken: In a bowl, whisk the buttermilk with a pinch of sea salt, black pepper, and a teaspoon of paprika, then soak the chicken fillets in the mixture for at least 15 minutes. If using eggs, beat them with the same spices and use them to soak the chicken.
Coating The Chicken: Combine the wholemeal flour, remaining paprika, garlic powder, onion powder, and dried sage in a large bowl. Season with salt and pepper. Dip each buttermilk-soaked chicken fillet into the seasoned flour, ensuring a complete coat. Press gently to adhere. Roll the flour-coated fillets in the crushed puffed rice for an added layer of texture.
Frying The Chicken: Heat the oil in a large skillet or fryer to about 180°C (350°F). Carefully place the coated chicken fillets in the hot oil and fry until golden brown and cooked through, about 4-5 minutes on each side. Drain on paper towels.
Assembling The Sandwich: Toast the wholemeal buns lightly. Spread a generous amount of the yogurt dressing on the bottom half of each bun. Layer with shredded lettuce and sliced avocado. Top with the crispy fried chicken fillet, a drizzle of hot sauce if desired, and the top half of the bun.
Making The Yogurt Dressing: Mix the Greek yogurt, crushed garlic, and cider vinegar in a small bowl. Season with salt and pepper to taste. Refrigerate until ready to use.