Halibut With Lentils and Mustard Sauce

This is almost a good recipe, but didn't work for us.

• I made a half recipe, with halibut.
• The lentil with sweet potato bit was a bit bland.
• I cooked the fish under the broiler rather than sautéing it. No problem here.
• The sauce was really iffy, much too sharp. I have an idea there there is Dijon mustard and there is Dijon mustard. What I have is too strong to do in a 1:1 proportion with wine. On the other hand, it did liven up the lentils. (The rest will turn up as a salad dressing in the next days.)

I've made similar sorts of things that were much better, so probably won't try this again.