In a 3 litre (or larger), heavy-bottomed pan, heat the oil and popcorn over medium-high heat. Cover the pan and shake gently. Cook until all the kernels have popped, about 3 mins. Place the popcorn in the prepared bowl.
In a medium saucepan, heat the butter over low heat. Add the vanilla essence and marshmallows. Stir constantly until the marshmallows have melted and the mixture is smooth, about 5 mins.
Pour the melted marshmallow mixture over the popcorn. Using a spatula sprayed with cooking spray, stir until the popcorn is coated. Spread the mixture over the prepared baking sheet. Sprinkle with the chocolate bar pieces, cookies, almonds and sweets.
Using a spatula, gently press the toppings into the popcorn. Allow the mixture to dry for 1 hour.
Break into 5cm pieces and store airtight in a plastic container.
Serving Suggestion: Place in small plastic bags and tie with coloured ribbon for a pretty gift.