Preheat an oven to 170°c/150°c fan (338°f/302°f).
Lightly grease an 8" square baking tin & line with baking parchment.
Chop the butter into evenly sized pieces then place into a large saucepan. Place over a medium heat & cook, stirring regularly until the butter is brown & smells nutty.
As soon as the brown butter is cooked, take the pan off the heat then add in the golden syrup & sugar and mix until smooth.
Next, add in the oats, flour, salt, raisins, sultanas, pumpkin seeds, walnuts & almond extract.
Mix well then transfer the flapjack mix to the lined baking tin.
Use a palette knife to press the flapjack down into a flat, even layer then bake in the preheated oven for 20-25 minutes, until golden brown but still soft.
Once baked, leave the flapjacks in the tin, to cool completely then use a sharp, serrated knife to cut into 9 squares.