A hand beater on high works best, for sure. I was tempted to put it into my Kenwood but the bowl is too big, so I patiently stood with the hand beater! I found 15 min was quite enough, although the recipe says 15-20. I had the mixture in the pan by 6 pm, so I had to leave it for the next morning. Important to spray the knife and clean it with a paper towel between each cut and then spray again, or use coconut oil or butter.
I'm sure you'll have success with a hand beater!