To prepare cookies: Position rack in center of oven; preheat to 350°F. Line a large baking sheet with parchment paper or a nonstick baking mat (see Tip).
Process almonds in a blender in 2 batches until finely ground. Transfer to a large bowl and add flour, 1/2 cup butter, sugar and salt. Knead the mixture with your hands until well blended. (The dough will be dry.) Gather the dough into a ball; divide it into 2 portions.
Working with one portion at a time, roll the dough between 2 sheets of parchment or wax paper until 1/8 inch thick. Cut out cookies using a 2-inch circular cookie cutter. Using a metal spatula, place them 1/2 inch apart on the prepared baking sheet. (If you like, cut out the centers of half the cookies using a 1-inch cutter.) Gather the scraps, reroll and continue cutting out cookies until the dough is gone. Repeat with the second portion of dough. e the cookies, one batch at a time, until puffed and beginning to color, 8 to 10 minutes. Cool on the pans for 5 minutes before transferring to a wire rack to cool completely.
To fill & glaze cookies: Spread preserves on half the cookies; top with the remaining cookies to make sandwiches.
Melt chocolate and 1 tablespoon butter in a double boiler over hot water. Remove from the heat; stir in milk and corn syrup until smooth. Line 2 baking sheets with wax paper. Dip each sandwich cookie halfway into the chocolate, then place on the wax paper. When all the cookies are dipped, refrigerate until the chocolate has set, 20 to 30 minutes.