This is not a typical cake texture—it is fudgy, extremely moist, and brownie-like around the edges. It pulls together swiftly and ahead of time, and pleases pretty much everyone who ever comes to your table.
Butter a 9-inch round cake pan and line the bottom with parchment; also butter the parchment. Heat the oven, with a rack placed in the center, to 375 F.
Melt the chocolate in a double boiler (make your own by setting a bowl over a saucepan, without the bowl touching a few inches of water beneath in the pan). As the chocolate melts, add the butter a few tablespoons at a time, stirring constantly with a whisk.
When the butter and chocolate are all melted, remove the bowl from the double boiler, and add the sugar and whisk to combine. Add the eggs, one at a time and whisking well to incorporate each egg before adding the next one. The batter will look grainy but shiny until the last egg goes in, and then the batter will be smooth and silky.
Whisk in a pinch of salt and a tablespoon of flour, and pour the batter into the prepared pan, inhaling the chocolate scent as you go. Bake the cake for about 25 minutes, or until the top is crackly and the center no longer looks shiny. The clean-toothpick test doesn’t work here because the center of the cake remains fudgy. Cool the cake for about 10 minutes. Flip the cake out onto a plate, then flip it onto another plate so the crackly top is facing up. Dust lightly with powdered sugar.
While the cake bakes, place the raspberries in a bowl with a tablespoon of sugar, and mash up some of the berries with a fork. Whip the cream with a tablespoon of powdered sugar and the rose water. Swirl the raspberries into the cream.
I like to cut the cake into wedges at the table, with a bowl of the swirled cream right next to it. Anticipation is a great way to whet an appetite. A few extra raspberries on the plates when serving make a nice touch too.