Thats why I went to Tesco & got a tin of Ambrosia Devon Custard, to try and pick out all the flavours, I failed miserably hence buying the concentrates lol.. I do agree though..
But according to Nigella, (my very very favorite TV chef) her recipe is Cream, egg yolks, caster sugar, cornflour and a vanilla pod.. so the sweet, the Vanilla and the cream is all do-able but how do you get egg into it without a concentrate.?
there are 2 main types of custard.
there is the 'Birds custard' that's made with custard powder (which is cornflour, sugar, pretend vanilla and yellow colouring) almost noone ever cooks it enough when they make it and as a result it tastes 'powdery' (this is the taste from the uncooked cornflour). Lots of people think that this is custard and that's how it's supposed to taste.
then there is what's known as 'creme anglaise' or egg custard. It's made with milk/cream sugar egg and vanilla. It tastes very different to 'custard powder custard' although if you cook custard powder custard properly then the finished article is a lot closer.
Egg custard thickens as the heat when cooking it sets the proteins in the egg, which as you are whisking it lots while it cooks, form into long strands that tangle up and trap air. custard powder custard thickens because the starch in the cornflour joins into long strings which trap air.
there are several other types of custard, confectioners custard (creme patissierre) which is the custard that's in a Danish pastry, or a fruit tart, creme renverse (baked custard, which is what creme caramel is made from) you can get tinned custard, instant custard and more....
Egg custard is richer and creamier and is also naturally yellow because of the colour from the egg yolks.
So before you make custard liquid you nee to decide what custard you're aiming for.
the single best custard concentrate atm (in my opinion) is Capella. You can make really good DIY e-liquid with 15-20% Capella VC and a few drops of sweetener. You don't need dulche de leche or EM or other stuff. they also have a v2 out now which as well as having no Diacetyl in it also doesn't have AP in it either (which the original one does) AP is a similar compound to Diacetyl, though as yet it's not been proven to cause any harm, it might do and there are lots of people that recommend not using it.
My custard e-liquid used Steevos as a starting point. What I ended up with was different, I don't think any of the ratios are the same in my final recipe and I took out a couple of things and added a couple of other things. As it stands though Steevos is one of the better more complex custard recipes around. Being complex though it *needs* 2 weeks steeping time or it'll be horrible. My final recipe took me 15 revisions (each with 2 weeks steeping time between them) to get right.
Good luck in your custard making, but while it seems really simple, and while you can get good results from a very simple recipe, it's one of the harder flavours to get right. Or at least I found it that way.