Add the biscuits to a blender and blend until fine or place the biscuits in a ziplock bag and using a rolling pin, crush the biscuit until very fine. Add the butter to a medium sized bowl and place in the microwave. Heat until the butter has fully melted. Add the crushed biscuits and mix until fully combined.
Add the biscuits to your serving dish and gently press and spread the crumb mixture along the base and side of the dish. Place in the fridge while you make the filling. Note: use a spring form pan or glass dish, the springform pan will naturally ensure an easier release. If you want to be extra safe then line the dish with baking paper that overlaps the edge, allowing you lift the tart out of the dish.
Line the base and sides of a medium saucepan with 1 tbsp butter. Add milk, cream, condensed milk, cinnamon stick and vanilla essence and bring to a medium heat or until simmering. Meanwhile, prepare the egg mixture. Note: if the milk start simmering and the egg mixture isn't ready yet then remove the milk mixture from the heat. You don't want any unnecessary moisture evaporating.
In a medium bowl, add eggs and water. Whisk until fully combined. Add cornstarch and salt, whisking again.
Once the milk mixture is simmering, lower the heat and pour the egg mixture into the warm milk mixture whilst whisking. Continue whisking until the mixture thickens, about 2-4 minutes. Once the whisk start creating a pattern when whisking, you know it's ready. Note: Do not make the mixture too thick otherwise it'll struggle to adhere to the biscuit base.
Remove the base from the fridge and pour the custard in the base. Smooth the surface and finish off the cinnamon. Once the no bake milk tart has reached room temperature, you can cover the tart with cling wrap and place in the fridge to set for 4 hours or overnight.
Allow the tart to reach room temp before slicing. Geniet hom, tastebud!