Custard should taste eggy. This is a feature, not a bug. However, from your mention of flour, I think what you're talking about is a souffle, not something like a creme brulee or along those lines. Would that be correct?
Edited based on subsequent clarifications:
Ah. Your method is sorely lacking, and your ingredients are off. You need to temper the yolks first, you need to use yolks only, and use cream instead of milk. Here is a smaller version of what I use at work for creme brulee:
- 1L 35% cream
- 11 egg yolks
- 1C sugar
- 1 vanilla bean, scraped
Bring cream to a simmer with the vanilla seeds and pod (you can use approx 1.5tsp vanilla extract, pure not artificial, instead). While it is heating, beat the yolks and sugar together until just incorporated. Pour the cream into the eggs whisking briskly to prevent curdling. Pour mixture through a fine chinois. Skim off foam, pour into ramekins. Place ramekins in a pan, add water to 1/2way up the sides. Cover pan with foil. Bake at 275 (convection) or 325 (non convection) for approx 40 minutes, until wobbly in the centre but set. Chill until set, eat.
The deflation is caused by a souffle effect coming from including the egg whites, which are never used in a custard--custards, creme anglaise, etc, are always yolks only. When you include the whites, air will be trapped inside temporarily, and will escape/collapse when the mixture cools. If you bake until fully stiff with my method, you will get hard and rubbery custard by the time it is set in the fridge.
Also, save the whites--they freeze well--for meringues or souffles.
you need to make sure your souffle has an even cooking temperature.
1) dont open the door to the oven
2) make sure your oven tempature doesnt fluctuate widley
3) put the souffle inside a small pool of water. This helps to regulate the temperature better.
Best Answer
I've had this exact same issue when making Creme Brulee. If you heat the mixture too long it will turn to the consistency of scrambled eggs. I have figured out that if I gently jiggle the pan a few minutes before it is supposed to be set and you will see a slight wobble. Repeat this for the next few minutes until it wobbles less, then remove it immediately
This is the method that works best for me. There are so many variations due to the oven, altitude, number of eggs in your mixture, etc. to give you an exact time. It took me at least 15 tries to finally get my creme brulee recipe right but now I know what to look for when its done.