It's Christmas Crime! by Anouk Filippini, Trade Paperback

A teen working at a Parisian bakery witnesses a murder in this cozy holiday mystery with a dreamy romance at its center that’s a festive entry in the New York Times bestselling Advent Romance series, told in a perfectly paced advent calendar format with chapter-a-day reading.
When Suzanne Sécretant arrives in Paris for her apprenticeship at the prestigious Rivoli bakery, nothing goes according to plan—starting with her being stuck rolling croissants instead of learning from the whimsical head pastry chef and ending with her witnessing an actual murder. This was definitely not how she had intended to spend her holidays.
But after meeting the charming Léo and mysterious Sofiane, and armed with the victim’s last words, Suzanne realizes she might be the key to solving this case. And she could even find a little love along the way.
With this book’s unique advent calendar format, each of the twenty-four chapters is sealed by its own perforated enclosure that readers can gently tear open—by hand or with the help of a ruler—to read a chapter a day in the weeks leading to Christmas!