Place cubed softened butter along with the sugar and vanilla extract into a large bowl and beat for about 5 minutes or until pale , light and fluffy , then add the egg and beat until well combined , sift the flour custard powder together over the butter mixture in the bowl and using a wooden spoon mix till dough form , then knead a little , then flatten a little and wrap in plastic wrap and refrigerate for 15 or until needed .
Preheat oven to 180°C . Lightly grease muffin tray holes , or a small tart tray , then cut enough strips of baking paper to fill one per muffin hole , and place one thin strip of baking paper per muffin hole , making sure it reaches the bottom and over two of the sides of the muffin tray holes (makes for easy tart removal) and set aside until needed .
Take the prepared dough from the fridge and between two sheets of baking paper roll the dough out to about 5 mm thick , then using a cookie cutter to size , cut dough circles out to fit muffin tray holes fully .
Press prepared dough circles into the muffin tin holes , making sure you press them down to the bottom and all the way up the sides to the top . Place prepared dough filled trays into the Preheated oven and cook for 15 minutes till just done , then remove from heat and let them cool slightly .
Slice the strawberries , bananas or fruit of your choice up whilst the cookie cases are cooking .
Place some of the strawberry slices , or fruit of your choice slices , into the bottom of the prepared , cooked , cookie cases , till just under the top . Next add about a spoonful of the chocolate chips , or a piece of chocolate , ontop of the fruit slices in the prepared cookie cases .
Next add a mashmallow on to the top of the strawberries and chocolate in the prepared cookie cases , and make sure it's on the inside of the cookie case , and push down to secure it .
Place the prepared cookie filled trays into the Preheated oven and cook for a further 5-8 minutes or until marshmallow is melted and golden on top . Remove from heat and let cool slightly before removing from the tray .
Once removed from the tray , either serve warm on a serving platter or wait till they cool completely and serve , enjoy . :-)