From WP.,
Ingredients
7 ounces (200 grams) dark chocolate (60 to 70 percent cacao solids; see headnote)
14 tablespoons (7 ounces/200 grams) unsalted butter, plus more for greasing the pan
1 1/4 cups (250 grams) granulated sugar
5 large eggs, at room temperature
1 tablespoon all-purpose flour
1/4 teaspoon fine salt
Whipped cream, for serving (optional; see related recipe)
Fresh raspberries, for serving (optional)
Instructions
1. Position a rack in the middle of the oven and preheat to 375 degrees. Lightly butter an 8- or 9-inch round cake pan. Line the bottom of the pan with a circle of parchment paper, and butter the paper.
2. In a large bowl set over a pot with a little simmering water – don’t let the bottom of the bowl touch the water – melt the chocolate and butter together. (Alternatively, you can melt the chocolate and butter in a microwave on HIGH in 30-second bursts, stirring between.)
3. Remove the bowl from the heat and whisk in the sugar until incorporated. The mixture will look gritty.
4. Add the eggs, one at a time, whisking each one into the batter well before adding the next. The batter will look a little slimy; that’s okay.
5. Finally, whisk in the flour and salt until the batter looks thick and shiny. Transfer the batter into the prepared pan and bake it for 25 to 27 minutes, or until the top is shiny and a bit crackly. It should jiggle slightly in the center.
6. Transfer to a wire rack and let cool in the pan for 20 minutes before inverting it onto a plate and peeling the parchment off, then reverting it top side up. The cake will deflate a little as it cools; this is normal. Let cool until just warm or completely before slicing and serving with whipped cream and berries, if desired.