Line the baking tin with parchment paper and set aside. In a large mixing bowl, measure out the rice cereal, then set aside.
200 g (5 cups) rice krispies
In a large saucepan, place the butter and condensed milk, melting gently until smooth and combined. Tip in the marshmallows and continue to cook over a low heat until completely melted. Add in enough food colour to achieve a strong green as the colour will be less intense once combined with the rice cereal.
100 g (¼ cup + 3 tbsp) unsalted butter, 100 g (¼ cup + 1 tbsp) condensed milk, 275 g (5 cups) marshmallows, green food colouring
Tip the green marshmallow mixture into the bowl with the rice cereal. Working quickly, stir everything together until evenly combined, then tip the mixture into the prepared tin, smoothing into the corners and levelling the top. Leave to cool and set.
Once the rice krispy treats have set, remove from the tin and cut into 18 bars (3 rows of 6 rectangles) or however you wish to cut them.
Melt the dark chocolate, then dip the smaller top end of each bar into the melted chocolate. Shake off any excess, then dip the same side into the chocolate sprinkles whilst the chocolate is still melted so the vermicelli sticks to it.
75 g (½ cup + 1 tbsp) dark chocolate, chocolate vermicelli
Transfer the remaining melted chocolate to a piping bag and snip the end off. Use the melted chocolate to help stick two eyes and two bolts onto each Frankenstein rice krispy treat, then use the remaining chocolate to pipe on a mouth for each Frankie. Leave to set (or pop in the fridge for a few minutes to speed up the setting!) then dig in. Enjoy!
sugar eyes, chocolate fingers