Line 2 baking sheets with nonstick baking paper. Place the butter, honey or agave syrup, oats, vanilla extract and bicarbonate of soda in a saucepan over a low heat and warm gently until the butter has melted. Stir well, then leave to cool for 5 minutes.
Scrape the mixture into a large bowl and stir in the flour and sugar. Add the fudge chunks and mix until combined. Roll the mixture into 18–20 balls, then place on the prepared baking sheets and flatten gently.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 10–12 minutes until deep golden. Leave to cool on the sheets for 1 minute, then transfer to wire racks to cool and harden.