Step 1: Prepare the Base

1. Line an 8×8-inch (20x20cm) square baking pan with parchment paper.
2. In a bowl, mix the crushed biscuits, melted butter, brown sugar, and vanilla extract until combined.
3. Press the mixture firmly into the pan and refrigerate while making the marshmallow layer.

Step 2: Make the Marshmallow Layer

1. In a saucepan over low heat, melt the butter and condensed milk, stirring constantly.
2. Add the marshmallows and continue stirring until fully melted and smooth.
3. Remove from heat and stir in vanilla extract (and food coloring if using).
4. Pour the marshmallow mixture evenly over the biscuit base. Smooth with a spatula.

Step 3: Add Toppings & Set

1. Sprinkle with coconut, sprinkles, or drizzle with melted chocolate if desired.
2. Refrigerate for 2-3 hours or until firm.
3. Slice into squares and enjoy!