Claire Saffitz!
Dessert Person is her first and has some pretty challenging recipes. What's For Dessert is her second and is more approachable.
She's a great writer and the recipes are delicious. She also has this chart in the front of both books which I think is an amazing resource every cook book should have.
Just in case the photo doesn't work, it's a matrix of all recipes in the book plotted on a x-axis of time to complete and a y axis of difficulty.