Process the granulated sugar and salt in a food processor until it looks powdery and a little finer, 30 to 60 seconds. Add the almonds and process until they are finely chopped, about 20 seconds. Add the butter and the vanilla and almond extracts. Pulse until the butter is smooth, scraping the bowl as necessary. Add the flour and pulse until soft dough begins to form around the blade. Transfer the dough to a large bowl and stir briefly with a rubber spatula to be sure it is evenly mixed. Portion the dough into equal thirds. If you have a scale, weigh each third; each should weigh 10 1/2 to 11 ounces.

Make the thumbprints before chilling the dough. Scoop up a generous teaspoonful (2 level teaspoons) of the dough and shape it into a one-inch ball with your hands. Roll the ball in the coarse sugar and set it on a tray lined with waxed paper. Repeat with the rest of the dough, setting the balls slightly apart. Press a thumb or forefinger, dipped in flour, into each ball to create a depression. Cover and refrigerate the cookies for at least two hours, but preferably overnight.

Remove the cookies from the refrigerator and arrange them one inch apart on an ungreased or foil-lined cookie sheet. Position a rack in the center of the oven and heat the oven to 325 degrees. Let the cookies sit at room temperature while the oven heats. Bake the cookies for 10 minutes. Gently redefine the depressions with your thumb or the tip of a wooden spoon’s handle, if necessary. Rotate the sheet and continue to bake until the tops are lightly colored and the bottoms are golden brown, another 8 to 12 minutes. Transfer the cookies to a rack and let cool completely.

While the cookies cool, prepare the filling. Put the chocolate and butter in a heatproof bowl set in a wide skillet of almost simmering water, or in the top of a double boiler. (Or microwave on medium power for 1 to 2 minutes, stirring after the first minute.) When the chocolate is almost completely melted, remove the bowl from the heat and stir until completely melted and smooth. Spoon the filling into each depression. If the filling hardens while using, reheat it in the pan of hot water. Yields about 24 cookies

My novel about the importance of friendships has enlarged my own. I traded cookies for tales about the importance of cookie clubs to their members. In South Carolina, a cookie exchange is in its thirtieth year and includes grandchildren of the original members. A mother, now using a walker, asked her daughter to obtain a signed book for her at my reading in St. Joseph, Michigan. Fans, inspired to start their own cookie club, showed me pictures of smiling partiers, told me wonderful stories, and handed me many recipes.