Well, I've cooked a dozen feasts or so for Stormvale, plus a good many dishes for revels and what not. I could cook many more dishes without getting tired of the cuisine, but it occurs to me to consider what I actually need to work on.
First, I've never baked bread. Never even tried it. The topic is a complete mystery to me.
Second, candy-making. While I've cooked many period desserts of the pudding or tart variety, candy-making (other than chocolate truffles, which are both easy and entirely non-period) has always been a disaster. I've literally never successfully cooked a piece of medieval candy. Marzipan was a failure, orengat produced nothing edible, and sugar-coated spices... well, left me wondering about the relationship of any of the recipes to the physical world I live in. Even springerle cookies completely defeated me the first time I tried them. I may have a couple of problems here - I tend to cook recklessly, adding or subtracting here and there, using eye and judgment rather than strict adherance to recipe or temperature. But this is, I gather, not the attitude to take about candy. Temperatures need more exactness, I am told, time and quantities are not to be casually tampered with. Well, ok.
Third, pie dough. Ok, I'm impatient about pie dough. When you can buy it cheaply and get good quality (and note that you generally can't do that with the average medieval ingredient of any kind), it's hard to resist just moving on to something less annoying. The damn stuff just doesn't want to roll out the way I want it to. Practice makes perfect, I suppose.
So, three additional skills to master.