Preparation

• Brush twelve four-inch nonstick tart pans (preferably with removable bottoms) with melted butter and coat with flour or cocoa powder, tapping out the excess.

  Combine the butter, chocolate, and salt in a small microwave-proof bowl. Microwave on high for one minute, stir, and repeat for another minute or until the chocolate seems softened but still looks somewhat chunky. Remove from the microwave and stir to distribute the heat until the chocolate is completely smooth. (If you don’t have a microwave, you can melt the chocolate mixture over a hot water bath.) Let the chocolate mixture cool to room temperature.

  In the bowl of an electric mixer, combine the egg yolks with all but two tablespoons of the sugar. Beat on high speed with the whip attachment for about two minutes, until the mixture lightens in color and thickens in consistency. (If you prefer, you can whip the yolks and sugar by hand with a whisk.) When you lift the whip, the batter should fall back into the bowl in ribbons. Fold the cooled chocolate mixture into the egg yolks with a rubber spatula until the mixture is evenly mixed. Transfer to a bowl and set aside.

  Thoroughly clean and dry the stand mixer’s bowl and whip attachment. In the bowl, combine the egg whites with the remaining two tablespoons of sugar and whip at high speed just until they form soft peaks. Don’t overbeat the eggs or they’ll get dry and grainy.

  将蛋清的三分之一oop放入巧克力混合物中，并使用橡胶刮刀或大搅拌器将混合物折叠在一起，将混合物折叠在一起，直至将蛋清均匀地掺入。Then add the remaining egg whites and lightly fold them in. Be sure to fold gently—if you stir too roughly, you’ll knock the air out of the mixture, decreasing the volume of the batter and leaving you with fewer tarts than you had planned. Spoon the batter into the prepared tart pans so that the batter reaches about 1/2 inch from the top. Cover the tarts with plastic wrap and refrigerate until you’re ready to bake them.

  Heat the oven to 475°F. If you’ve prepared the tarts ahead of time, take them directly from the refrigerator to a baking sheet and put them in the oven. Bake until the tarts jiggle like firm gelatin, and you still see a spot or two of liquid batter on top, 9 minutes if the batter has been chilled, or 8 minutes if you’re baking them right away and the batter is room temperature. Loosen the tart by running a knife around the edges. If your tart pans don’t have removable bottoms, cover the tarts, one by one, with a clean plate or baking sheet, flip over the tart pan, and shake gently to release the tart from the pan. Serve immediately.