Place the olive oil into a frying pan, add the rosemary and place over a low heat. Allow the oil to heat up and as soon it starts to simmer, remove from the heat and pour the oil into a heatproof bowl.
Drain the bocconcini balls and placing them in a separate bowl with the chili flakes. Shake gently to ensure each ball has a little chili on it, then set aside.
Cut the pineapple into 20 small chunks (or if using tinned just drain the pineapple).
Place your frying pan back on the heat (no need to wash it) and add the pineapple. Cook over a high heat for 2 minutes then flip and cook on the other side for a further 2 minutes. Remove from the heat and tip the pineapple into the warm rosemary oil. Allow to cool.
Take 20 cocktail sticks (or branch) and push on a baby bocconcini ball. Add a chunk of pineapple and set onto a platter.
Cover and keep chilled until serving. Remove them from the fridge at least 15 minutes before you want to eat them.