Yes, after you are 100% practiced, you need to add all the special ingredients. There is a huge list of them. Basically, I went to all the shops and bought every single ingredient they offered. Then checked all of them for the contest. You'll know you've got it all when the bars are all 100% in the contest. The first time I tried this, I couldn't get the number and it turned out that I didn't have any potatoes. Seriously, just buy everything. You should be able to afford it. Once you're at 100% on everything, you don't even need to play the mini-games. Just sit back and watch. I don't think you can win without getting it 100%.