Rhubarb Creme Brulee

In flavour, this clearly was a 5 star dessert. The rich custard that perfectly complemented the flavour of the rhubarb, the crunchy sugar - just brilliant.

The only problem was that the custard didn't get firm, and I'm not exactly sure, why. I might be that we didn't cook it long enough, though I thought we did. I noticed that other recipes such as the very similar one in Flavour First cook the custard au bain marie a second time once it has been filled into the ramekins. To be honest, if possible I would rather try to avoid this, I remember doing it once and thought that it was such a hassle, and with the shallow creme brulee ramekins it'll be an extra hassle. Instead, I was wondering if I could cheat next time by adding a little gelatine .