Prepare your dish: Line a 20cm x 20cm square baking tin with a sheet of baking paper, leaving some overhang on two sides so you can lift the finished block out easily. Lightly grease the paper with a dab of butter.

Melt the butter: Place your large saucepan or deep frying pan over a low heat and add the dairy-free butter. Watch it slowly melt into a golden puddle — you will see small bubbles form around the edges, and the butter will smell nutty and warm. This takes about 2 minutes.

Add the marshmallows: Tip the entire bag of vegan marshmallows into the melted butter. Stir constantly with a wooden spoon or silicone spatula. The marshmallows will first look lumpy and opaque, then gradually soften into a glossy, stretchy mass that pulls away from the sides of the pan. You will hear a gentle bubbling sound as they melt. This takes about 4-5 minutes.

Remove from heat and add flavour: Take the pan off the hob immediately. Stir in the vanilla extract and salt. The mixture will release a sweet, creamy aroma that fills the kitchen. If you are adding chocolate chips, coconut, or crushed raspberries, fold them in now.

Fold in the cereal: Pour the crispy rice cereal into the pan all at once. Using a folding motion — lift the marshmallow mixture from the bottom and turn it over the cereal — work until every grain is coated. You will see the cereal turn from pale beige to a uniform golden colour, and the mixture will feel heavy and slightly resistant to the spoon. Work quickly but gently; you want to coat the cereal without crushing it into dust.

Press into the tin: Scrape the mixture into your prepared baking tin. Lightly wet your hands with cold water (this stops the mixture sticking to your fingers) and press the treats into an even layer. Press firmly into the corners and flatten the top. The surface should look smooth and even, with no gaps showing the paper underneath.

Cool and set: Leave the tin on the counter for at least 30 minutes. Do not put it in the fridge — rapid cooling can make the treats turn hard and brittle. You will know they are ready when the top feels firm to the touch and the block lifts cleanly from the paper when you pull the overhang.

Slice and serve: Lift the block onto a cutting board. Use a large, sharp knife to cut into 12 even squares. You will hear a satisfying crackle as the knife goes through the crispy rice layers. Serve immediately or store for later.