Pair up the biscuits in 2 rows (like a sandwich line) so they can be sandwiched together at the end.
Cut 2 marshmallows in half, per sandwich, which gives you 4 marshmallow halves per biscuit. Put the sticky (cut) side of the marshmallow onto one of the paired biscuits and arrange on a lined tray.
The other biscuit pair needs to be spread with plenty of jam - to make it smoother, you can warm it in the microwave if required. Don't put these on the tray.
Once the oven is at the correct temperature put in the tray with the biscuits topped with marshmallow. Watch them closely - we want them to just start to melt.
Once marshmallows have started to melt, remove them and put the partnered biscuit with the jam on top. DO NOT PRESS. Yes it will ooze out the side but don't worry. Set aside and allow to cool for approximately 20 minutes.
Place chocolate buttons into a large glass or stainless steel bowl. Find a saucepan that the bowl will be able to sit on and fill until it has approx 4cm depth of water. The chocolate in the bowl should not be touching the water or the bottom of the saucepan. Put saucepan onto a simmer and stir the chocolate until it has melted.
Once chocolate has melted take it directly off the heat and add in the oil, stirring. You may need more oil - the oil makes a thinner chocolate spread.
Dip the biscuits in the melted chocolate (I find two forks help with this process) and then put onto baking tray with non stick baking paper. Sprinkle with hundreds and thousands and put in the fridge to cool. Eat and ENJOY :)