First off..
nekocat said:
Should be "If I was the author" or you could say "If I'd written this"
Now.. to the question at hand..
"I did not remember that I had minced it up so fine".. must be broken into two parts. To be honest it's one of those sentences that sounds stranger the more you say it aloud, but, sounds okay the first time you read it.
I did not remember.. = I didn't remember
So the sentence is indicating that the act of not remembering happened in the past. It's a simple past strucutre. I did not eat, I didn't sleep, I didn't remember.
I had minced it so fine.. = I'd minced it so fine
It's a past perfect sentence, indicating that the act of mincing has finished. Other examples.. I had stopped, I had not pushed, etc.
As someone else pointed out, these days you'd say "I didn't remember mincing it so fine" or "I don't remember mincing it so fine", depending on when you're doing the remembering. And that is very acceptable.
However because we use the verb 'remember', the word 'that' can be inserted. I do not know the grammatical term for this kind of structuring, maybe someone else can chime in here, but when you have a thinking or saying verb such as tell, say, think, remember, recall, etc., you can use reported speech and the word 'that' to be more formal.
"I didn't think that she'd heard me talking to her sister"
"I shouldn't have said that the movie was boring"
"I seem to recall that you said you were moving to Tokyo"
So in combining the two, we have the speaker reporting on themselves.
"I did not remember that I had minced it so fine".
It IS akward, but it's not incorrect as far as I can tell. Using perfectly formal syntax sometimes results in akward but correct things.