Place the Boneless Skinless Chicken Breast in a pot with enough Water to cover, add a Bay Leaf and a pinch of Salt, then simmer until the chicken is very tender (about 20–30 minutes). Reserve the cooking liquid and remove the chicken to cool.
Shred the cooled chicken finely with two forks or by hand.
Heat a splash of Olive Oil in a skillet, add chopped Onion and minced Garlic and sauté until translucent. Stir in diced Tomato, then add the shredded chicken, a grind of Ground Black Pepper and a pinch of Annatto Powder for color. Cook briefly to blend flavors.
Finish the filling by stirring in chopped Parsley and sliced Green Onions. Taste and adjust seasoning with more Salt or pepper if needed, then remove from heat and let cool.
Pour about 2 cups of the reserved chicken liquid (or use Chicken Broth if you need more) into a saucepan and add equal parts Milk and a knob of Unsalted Butter. Heat until the mixture comes to a gentle boil, season lightly with Salt.
Remove from heat and quickly stir in the All-Purpose Flour all at once, mixing vigorously until a smooth, cohesive dough forms and pulls away from the pan. Return briefly to low heat to dry the dough slightly, then transfer to a bowl and let it cool enough to handle.
When the dough is cool, knead it briefly on a clean surface to make it smooth. Pinch off portions and flatten each into a small disc. Place a spoonful of the chicken filling in the center and shape into the classic teardrop or drumstick form, sealing the seams well.
Set up a breading station: lightly flour the shaped coxinhas (use more All-Purpose Flour if desired), dip into beaten Eggs mixed with a little Milk, then coat thoroughly with Fine Breadcrumbs.
Heat enough Vegetable Oil in a deep pan to deep-fry (about 170–180°C / 340–360°F). Fry the coxinhas in batches until deeply golden and crisp, turning as needed, about 3–5 minutes per batch.
Transfer fried coxinhas to paper towels to drain. Serve warm and enjoy immediately while crisp on the outside and tender on the inside.
