Prepare the filling

1. In a large skillet, heat olive oil over medium heat. Add white onion and cook, stirring occasionally, until soft and translucent (about 2 minutes). Add garlic and cook for about 1 minute.
2. In a large bowl, combine shredded chicken, cooked onion and garlic mixture, salt, pepper, red pepper flakes (optional), mayonnaise or Catupiry cheese, and green onions or chives. Set aside.

Prepare the coxinha dough

1. In a large, non-stick saucepan, combine chicken stock, salt, annatto or turmeric (optional), and olive oil. Bring to a simmer over medium-low heat.
2. When hot, add sifted flour all at once, stirring vigorously for about 1 minute until a uniformly lumpy dough forms.
3. Remove from heat and transfer dough to an electric mixer fitted with a hook attachment. Knead at speed “2” for about 5 minutes, or until soft and smooth. If using a hand mixer, let dough cool enough to handle and knead well.
4. Scrape dough onto a well-floured surface and knead a little more by hand. Shape into a flat disk and let rest for 5 to 8 minutes at room temperature.
5. Roll out dough to ¼ to ?-inch thickness. Cut out 3-1/4-inch disks and place on a baking sheet lined with parchment paper.
6. Scoop about 1 tablespoon of chicken filling onto the center of each disk.
7. Lightly oil your hands and shape disks into drumsticks, pinching and sealing the edges. Pull the dough at the top out slightly to resemble a drumstick.
8. Use a moist towel to clean your fingers after each coxinha. Ensure no cracks; if cracked, wet fingers and pinch together. Flatten the bottom slightly so they rest upright.

Dredge coxinhas

1. Prepare three bowls: one with all-purpose flour, one with half the egg whites (4 egg whites mixed with 1 teaspoon of water), and one with half the breadcrumbs (about 1-1/2 cups). Pass coxinhas through flour, egg whites, then breadcrumbs, shaking off excess.

Fry coxinhas

1. Pour enough vegetable oil into a frying machine or heavy-bottomed pot. Heat to 350°F (177°C). If using no thermometer, dip a small piece of dough into the oil; a sizzling sound indicates readiness.
2. Fry in batches, ensuring not to overcrowd the pot. Turn to brown evenly.
3. Transfer coxinhas to a baking sheet lined with paper towels to absorb excess oil. Keep warm in the oven until serving.
4. Serve coxinhas with ketchup, lime wedges, rosé sauce, or chimichurri sauce.