Adjective for someone who is really good at cooking or baking and/or bakes frequently
So and so is the most "bakiest" person I know! She's so good at baking!
What word could feasibly replace "bakiest" which I obviously made up. :)
Solution 1:
When it comes to baking, she takes the cake!
Surpass or exceed all others [Oxford Dictionaries Online]
Solution 2:
She is a master baker (or bakeress).
You could also use the female equivalent, mistress, which Wiktionary defines as
5). A woman well skilled in anything, or having the mastery over it.
She is a mistress in the kitchen
It has the added advantage of sounding a little naughty too!
Solution 3:
The general adjective would be dexterous (or dextrous) because you need skilled hands to be good at cooking and baking. Dexterous is not usually used directly to describe a person who is good at cooking, it is used to emphasize cooking skills within the context; so it wouldn't be an exact fit for your example but you can rephrase your sentence.
Showing or having skill, especially with the hands
[oxforddictionaries]
Example usages from Google Books:
No one could have imagined that cooking could be a key aspect of dramatic attraction: this drama details cooking procedures from selecting and preparing materials to cutting, steaming, and decorating the food, all presented in fast changing close-up shots catching the colorfulness of the food and the cook's dexterous skills, accompanied by cheerful music and sound effects.
[Cultural Studies Of Transnationalis edited by Handel Kashope Wright, Meaghan Morris, Professor of Cultural Studies Meaghan Morris - 2013]
There was a certain artistic quality to the precise movements of the bakers upstairs, the way they pushed slats of “doughs” into the ever-rotating carousel inside the ovens, and then flipped them, and then later removed them, but Rick assured me that Mr. H was the best, fastest, most dexterous baker at H&H and that he had once stayed up for twenty-four hours helping bake a special order, which then he single-handedly drove down to Philadelphia on no sleep.
[How to Be a Man: Scenes from a Protracted Boyhood By Thomas Beller - 2010]
It is true, the teppan restaurants, in which diners sit around a large flat griddle table where foods are cooked by a dexterous chef, were first introduced to Japan after World War II as an attraction for Western visitors.
[Chicago's Best Restaurants by Sherman Kaplan - 2003]
Example usage from news articles:
Fortunately, this dexterous chef made some time to share his recipe for Belly & Trumpet’s watermelon salad with cashew relish.
http://www.thedailymeal.com/ask-dfw-expert-best-easy-tailgate-food
The sensational version at ROOF on theWit Hotel toes the line between timeworn and modern, all thanks to dexterous pastry chef Toni Roberts, who proves time and time again that she is one of Chicago's craftiest dessert mavens.
http://www.diningchicago.com/articles/2014/08/13/sweet-of-the-week-mint-chip-sundae-at-roof
You can also consider the informal British term dab hand. [The adjective form is dab-handed but it is very uncommon.] It means a person who is very good or expert at doing something. So in our context, the common phrases are:
dab hand in the kitchen
and
dab hand at cooking
It is worth to mention this usage because it is both related to skilled hands and expertise. It is a British term but it gained usage in American English also.
Example usages:
James is a dab hand at cooking main courses, meats, vegetables and such. His wife, Sarah, bakes like an angel and makes the most amazing pastries, breads and desserts.
[Seeking Truth by Francesca Hawley - 2009]
It could well be because of her dab hand at cooking great and tasty meals, that memories of being hungry for longer periods fade to the back of my memory, as mother had a definite gift of preparing delicious plates of food for us.
["The Journey of I & I" By Jah siSTAR - 2013]
Devoted to his mother—a stout, forceful hospitality-aholic who laid out stunning buffets of home-prepared breads, salads, cold dishes, roasts, soups, cakes, and sweets for her friends and neighbors—Beard had become a dab hand in the kitchen at a young age; by the time he was eight, he was baking his own bread.
[The United States of Arugula: The Sun Dried, Cold Pressed, Dark Roasted, Extra Virgin Story of the American Food Revolution By David Kamp - 2009]