Soak the tortillas in the milk for 15 minutes.
Combine the tortillas and milk with the onion and garlic in an electric blender or food processor and process until smooth.
Combine with the cheese, eggs, salt, and pepper and stir until thoroughly combined.
Roll into small balls.
Meanwhile, bring the chicken stock to a simmer over moderate heat.
Stir in the tomato paste and optional cayenne.
Add the tortilla balls and simmer for 10 minutes.
Calories: 124kcal | Carbohydrates: 6g | Protein: 11g | Fat: 6g | Saturated Fat: 4g | Polyunsaturated Fat: 0.3g | Monounsaturated Fat: 2g | Cholesterol: 18mg | Sodium: 917mg | Potassium: 193mg | Fiber: 0.4g | Sugar: 4g