1/4 to 1/2 tsp
POSITION rack in centre of oven, then preheat to 300F. Line 2 baking sheets with parchment paper.
DRAIN and rinse maraschino cherries in a sieve. Dry well with paper towels; set aside.
STIR ground almonds, flour and salt in a medium bowl.
USING an electric mixer on medium, beat butter with sugar in a large bowl until fluffy, 1 to 2 min. Beat in egg yolk and almond extract, scraping down side of bowl as needed. Gradually beat in almond mixture until just combined.
SCOOP 2 tsp portions and roll each into a ball. (Dough will be slightly sticky.) Flatten each ball on your palm, then wrap around 1 cherry. Roll into balls. Arrange on prepared sheets. Refrigerate until dough is firm, about 15 min.
BAKE until cookies are golden, 20 to 22 min. Transfer cookies to a rack to cool completely.
SET rack with cookies on a baking sheet. Temper chocolate and cacao butter. (If using white chocolate, stir in red food colouring until desired shade of pink.)
SPOON chocolate over cookies to coat completely, then top with 1 sliced almond, if desired. Let stand for 5 min, then use a spatula or palette knife to transfer cookies to a parchment paper–lined baking sheet. Let stand until chocolate is firm, about 30 min.