Line a baking pan with a baking mat or parchment paper; set aside.
In a medium bowl, whisk together the flour, baking powder, and salt; set aside.
In a large bowl, use an electric mixer on medium/high to cream together the sugar and butter, until mixture is light and fluffy, about 2 minutes. Beat in the ricotta, egg, and one teaspoon of almond extract, and mix until combined. Add in the flour mixture and mix until just combined.
Cover the cookie dough and chill in the refigerator for at least 2 hours.
Preheat oven to 350 degrees. Remove cookie dough from refigerator and use a cookie scoop to measure out about a tablespoon of batter and roll into a ball. Place on prepared baking sheets leaving about 2 inches between cookie balls.
Bake for 12-14 minutes or until the bottom of the cookie starts to brown slightly. Note that the cookies will not change color much. Cool in pan for 5 minutes before removing to wire rack to cool completely.
To make the glaze, in a small bowl whisk together the powdered sugar, milk, and ½ teaspoon of almond extract. Hold the cooled cookie upside down and dip the top of the cookie in the glaze. Return to the wire rack to dry completely. Sprinkle with sliced almonds if desired.
Notes
These Almond Ricotta Cookies can be made ahead and stored in an airtight container in the refrigerator for a week, or in the freezer for up to a month.