Tarte aux Quetsches et Crème de Noix

Name: Tarte aux Quetsches et Crème de Noix
Ingredients: For the pâte sablée:; 75 grams (1/3 cup plus 1 tablespoon) sugar (i use unrefined cane sugar, but regular white sugar is fine); 150 grams flour -- if you use american all-purpose flour, use 1 cup plus 2 tablespoons; 75 grams butter (i use salted, but you can use unsalted and add a pinch of salt) -- if you use regular american butter (which has less butterfat than european butter), use 7 tablespoons; Ice-cold water or milk; For the filling:; 135 grams (1 1/4 cups) shelled walnut halves; 2 tablespoons sugar (i use unrefined cane sugar; regular white sugar is fine, honey would be lovely, too); 1 egg; 3 tablespoons crème fraîche (substitute sour cream); Optional flavoring: 1 teaspoon pure vanilla extract, or 1 teaspoon plum or walnut liqueur, or 1 teaspoon light rum; 700 grams (1 1/2 pounds) ripe quetsche plums (substitute any other variety of plum)