Portuguese-Style Chicken Burger

While the fries are baking, drain the pineapple slices. Heat a large frying pan over a high heat. Cook the pineapple until lightly charred, 2-3 minutes each side. Transfer to a plate.

Thinly slice the red onion. Return the frying pan to a medium-high heat with a drizzle of olive oil. Cook the onion, stirring, until softened, 5-6 minutes. Reduce the heat to medium, then add the balsamic vinegar, water and brown sugar and mix well. Cook until dark and sticky, 3-5 minutes. Transfer to a bowl.

While the onion is cooking, finely chop the garlic. Place your hand flat on top of each chicken breast and use a sharp knife to slice through horizontally to make two thin steaks. In a medium bowl, combine the garlic, the salt, a drizzle of olive oil and a pinch of chilli flakes (if using). Add the chicken and toss to coat. Return the frying pan to a medium-high heat with a drizzle of olive oil. When the oil is hot, cook the chicken until lightly browned and cooked through, 2-4 minutes each side (depending on size). Remove from the heat and set aside to rest. TIP: The chicken is cooked through when it's no longer pink inside.

Bake the butter burger buns directly on a wire oven rack until heated through, 3 minutes.