Preheat oven to 375 degrees F. Line a baking pan with parchment paper and set aside.
In a medium bowl, mix flour, baking soda, baking powder, salt. Set aside.
Using a standing or handheld mixer, cream together butter and sugars until combined. Add the egg and vanilla and beat until fluffy.
Mix in the dry ingredients until combined.
Transfer to a work surface to knead the dough. Knead the dough for about 6 to 7 minutes, add a little milk at the time to make sure the dough is properly hydrated. Around 1/2 cup.
The dough is ready when it's not sticky and it doesn't crack when forming the corico.
Shape the coricos: When the dough is ready, divide the dough into 16 equal pieces. (Just eyeball it or weigh them to 35g each. Shape each piece into a ball.
Using your hands, shape the dough into a rope that is 5 to 7 inches long and gently press the ends together to make a ring or doughnut shape. Place the shaped cookies onto a baking sheet that has been prepared for baking.
Bake the cookies for 20 to 30 minutes, until they feel set and the bottoms are golden brown.
Remove the cookies from the oven and cool them right on the pan for 5 minutes. Then transfer to a cooling rack to cool completely.
Notes
Store these coricos in an airtight container at room temperature for up to 5 days, or in the freezer for up to 2 months.