Preheat the oven to 180C/350F/Gas 4. Grease and line a baking tray with greaseproof paper.
In a bowl, mix together the flour, sugar, porridge oats, butter, golden syrup and bicarbonate of soda mixture in a bowl to form a thick batter. With damp hands, roll portions of the mixture into 3cm/1½in balls and place onto the prepared tray, leaving plenty of space between each ball.
Flatten each ball with a fork, then bake in the oven for 15-20 minutes, or until golden-brown and cooked through. Remove from the oven and allow to cool.
Meanwhile, place the fudge between two sheets of greaseproof paper and roll out until the fudge is about 2mm thick. Cut into circles the same size as the oat biscuits and place over the top of the biscuits.
Pour melted white chocolate over the biscuits and fudge (you may want to do this by placing the biscuits on a cooling rack with some greaseproof paper underneath to catch any dripping chocolate).
Chill the biscuits in the fridge until the chocolate is set. Serve at room temperature.