Start by warming your milk on low to medium heat until it starts simmering
Remove it from the heat, cut the vanilla pod in half and keep it in the milk for an hour
Remove your vanilla pod and pour all of its grains in the milk and mix with a wooden spoon
Put your gelatin sheet in the bowl of cold water and let it absorb water for a good 15 mins
Beat the egg yolks with a whisk in a bowl
Add the sugar and whisk well
Pour the flour and continue whisking
Add the corn starch and whisk the mixture
Now, put the milk on medium heat until it starts boiling
As soon as it reaches its boiling point, remove the milk from the heat, pour 1/3 of the milk in the egg yolks, sugar, flour and corn starch mixture and whisk very well
Put back this mixture in the milk pot, put the pot back on medium heat and keep stirring. At this point you are cooking the cream
Then keep stirring until the cream thickens
Once you get a good creamy texture, remove the pot from the heat
Add right away the butter to the cream and whisk very well
Pull the gelatin sheet out of the water and squeeze it very well in order to drain it
Add it in the cream and mix very well
When everything is well mixed together, pour the cream in a clean stainless steel mixing bowl
Cover the newly obtained cream with a cling film, making sure it comes in contact with it to avoid any crust formation
Finally let it cool for some time (25-30 mins) until you can put it in the fridge (1 hour at least)