Irma Rombauer’s instructions for ‘Orange Filling’ (aka custard, but not really, since her actual orange custard recipe comes later and includes sectioning whole oranges) are as follows:
Stir and cook in a double boiler until thick:
1/2 tsp grated orange rind
1 tbsp lemon juice
6 tbsp orange juice
1/3 cup water
1/2 cup sugar
2 tbsp flour
1/8 tsp salt
3 egg yolks
I doubled it to fill my Egg Yolk sponge cakes. It didn’t have the butter or as much orange zest as ‘Orange Filling II’, but it was easy and it was going to do the trick. Besides, I was going to inject the calorie-clogging-ness into the buttercream, so might as well keep the dietary hurdle of the custard recipe to 6 egg yolks.
So I stirred and I cooked, and it took much longer than a normal custard. there wasn’t a point where I was stirring gently and it suddenly got a lot thicker and then I waited 45 seconds and then took it off the heat. It just very slowly thickened and I had to stir pretty regularly, even constantly near the end.
The filling implies a knowledge of how to set up a double boiler using a saucepan and a bowl, but some people don’t know how to do this. Apparently it was standard in 1948. We’ve lost so much of our culture…
…I actually felt good about this because my bowls are almost that old. These babies are work-horses. They’re meant for high heat like this. If you don’t have a bowl that you can rest on a saucepan (either because it’s plastic or another melt-able or heat-breakable material) then you’re kind of SOL.
About 25 minutes later(!) it was thick enough, and I took it off the heat to cool while I made the buttercream and waited for my egg yolk cakes to cool as well. I had just used 12 egg yolks in the course of an hour for 1 cake and I wasn’t even done yet. I was done with eggs, thank goodness.