It's a strange one this. I've had a run of bad base sauces in the past few months.
I made stew's (admin) base a good few nmonths ago now and it turned out bitter which it seems it also did for a good few others that tried it. But of course there were as many (or maybe more) who tried it and found it a great base, totally lacking in bitterness.
I then tried Smopkenspices base (the original unadjusted one) and that had some bitterness to it too.
My latest was the rajver base and I was expecting great things from this as it has had many favourable reviews, but it turned out to be the worst base I've ever made. I actually threw it away when only half finished, something I've never done before, it was just so bitter.
Now I've been racking my brains to see what I'm doing to end up with bitter results, but I just can't fathom it. I'm using exactly the same spices, pots, etc. that I have alway used. The only thing I know I did differently in the last two was use red onions and Tesco value onions, not the white (brown skin) medium sized onions that I would normally use. I'll revisit one of the bases eventually and use white onions and see what happens.
It just seems very odd that after what must be in excess of 100 pots of base sauce made over the years, all without any bitterness, I have three bad results on the trot. All very weird!