In a bowl, whisk together the flour, baking powder, and salt; set aside.
In a separate bowl, use a handheld mixer to mix together the butter, sugar, and ricotta cheese. Mix for about 2 minutes until light and fluffy. Add in the egg and vanilla, and mix until just combined. Pour in the flour mixture and mix until combined.
Cover the mixing bowl with plastic wrap and chill in the refrigerator for at least 2 hours or up to 24 hours.
When ready to bake, preheat oven to 350 degrees. Line a baking sheet with parchment paper or a nonstick baking mat. Use a cookie scoop to roll out balls of dough and place on cookie sheet leaving about two inches between each cookie (you should be able to get a dozen cookies on each baking sheet.).
Bake for 12-13 minutes, or until the cookie starts to puff up. Be careful not to over bake. Let cool on baking sheet for 5 minutes, then transfer to wire rack to cool completely.
Once the cookies are completely cooled, spread about a tablespoon of Nutella on the flat part of one cookie and use another to sandwich it in. Sprinkle with powdered sugar if desired.
Notes
Use softened room temperature butter so that it mixes evenly with the other ingredients.
Whole milk ricotta is the best, but part skim can be used if needed.
If your ricotta appears wet, just drain it over a fine mesh sieve to remove some excess moisture before using.
Be sure to chill the dough before baking. This will make the cookies easier to roll and prevent spreading.
Cool the cookies before adding on Nutella spread.
Dust the top of the cookies with powdered sugar for a festive look.
Nutella Sandwich Cookies can be stored in an airtight container in the refrigerator for up to a week.