Preheat the oven to 160°C. Grease a 6-inch loaf tin and line with baking paper and set aside.
In a bowl, mix the caster sugar, melted vegan spread, vanilla extract, cocoa powder, salt and baking powder.
Once combined, fold in the flour, then add in the milk and melted dark chocolate and mix until combined.
Chop up the marshmallows into smaller, bite-size chunks.
Add the marshmallows, chocolate chunks and roughly crushed digestive biscuits into the batter. Stir to incorporate.
Transfer the mixture into the tin, level the top with a spatula and bake for around 20-24 minutes.
Cool completely before cutting into squares. These brownies taste delicious on the day they're made and even better the following day!
