i make a baked custard its:
1 egg
1/2 cup of milk
1 tsp of sugar ( you can add more if you wish)
i also add either pureed apple, diced banana or sultana, optional extra though

whisk egg mik and sugar pour into a ramakin (over added fruit etc..)
place ramekin into a dish, pour boiling water into dish so it comes up about half way on the ramekin then bake in the oven till golden brown and set