In case you want to try it out:
In that recipe it says to use unsweetened condensed milk. In the UK, we only have sweetened which is thick, pale yellow and very sweet. I looked up unsweetened condensed milk and it is the same as evaporated milk. The taste of evaporated milk is completely different to condensed milk, and appearance wise, it is off-white and runny. It used to be used years ago as a substitute for milk in coffee. Is this what you used?
I wonder if I didn`t add too much whisked egg white.
That would definitely put lots of air into it. I wonder what it would be like without the addition of egg whites. It would certainly be denser. BTW, it also mentions adding 1 budyń in that recipe. Is that just the powder not mixed with milk? I have used budyń before in desserts but have made it up with milk as you would for custard, which is basically what it is.