My friend Marie-Hélène Brunet-Lhoste is a woman who knows her way around food. She's a top editor of the Louis Vuitton City Guides (and one of the restaurant critics for the Paris edition), so she eats at scores of restaurants every year, and she's a terrific hostess, so she cooks at home often and with great generosity. There's no question that she's a great home cook, but for me, she's the most frustrating kind of cook: she never follows a recipe (in fact, I don't think there's a cookbook to be found on her packed bookshelves), never takes a note about what she does, and while she's always happy to share her cooking tips, she can never give you a real recipe—she just doesn't know it. I've watched her in her kitchen, in the hopes of nabbing a recipe by observation, but it's impossible. Like so many really good cooks, Marie-Hélène starts off with a set of ingredients that could be annotated and recipe-ized, but, once she starts mixing, stirring, boiling, baking, or sautéing, she makes so many mid-cooking adjustments that you just have to throw up your hands and content yourself with being the lucky recipient. And so it was with this apple cake, which is more apple than cake, rather plain but very appealing in its simplicity (the chunks of apple make a bumpy, golden top) and so satisfying that we all went back for seconds. Despite knowing that it was futile, I asked for the recipe, and, of course, Marie-Hélène didn't really know. "It's got two eggs, sugar, flour, and melted butter—oh, and rum," she said. "I mix the eggs and sugar together and then I add some flour, some butter, some flour, and some butter." When I asked how much flour and butter, I got a genuinely apologetic shrug, and when I asked what kind of apples she used, the answer was, divers, or different kinds. Since there were only a few major ingredients, I thought I could figure out the recipe—and I did! (Although not on the first—or second—shot.) I've added baking powder to the mix (and I have a feeling Marie-Hélène might have too) and a drizzle of vanilla, which you can skip if you want. What you don't want to skip is the pleasure of having diverse apples. It's really nice to mix up the fruit, so that you have some apples that are crisp, some soft, some sweet, and some tart.