Panna Cotta Problems (NZ)

I've just started a new job as a pastry and prep chef at a restaurant that is opening soon so I've been in for a couple shifts to try out things.

The head chef gave me a recipe for panna cotta, it didn't set, he changed it up, and it didn't set again and he's blaming my technique rather than his recipe which I think is the problem.

These are all New Zealand ingredients.

First it was

750ml cream, 0.5 cup sugar, 1.5 leaves gelatin. Didn't work.

Next we tried 750ml cream, 150ml milk, 0.5 cup sugar, 2 leaves gelatin.

Heat liquid and sugar, steep flavour, bloom gelatin and dissolve in liquid that's cooled for 30 mins (but still warm), pot up.

He wants a really soft set panna cotta but he's blaming me rather than his recipe which I think is the problem, not enough gelatin, but I'm scared to make it again and have another stuff up.

I'm thinking take the second with the milk but use 5 or 6 leaves gelatin?

My only other job as a pastry chef was for 6 months about 2-3 years ago.