In a large pot, combine 4 cups of whole milk, 1 cup of granulated sugar, the cinnamon stick, the lemon peel, and the orange peel. Heat until it just begins to boil, then remove from heat and let sit for about 15 minutes.

Whisk together the cornstarch and flour in a separate bowl, then gradually add the remaining 0.5 cup of milk. Mix until completely smooth.

Strain the infused milk through a fine mesh sieve, return the liquid to the pot, and heat over low heat. Slowly incorporate the cornstarch-flour mixture, stirring constantly. Cook for about 6-7 minutes until it thickens.

Pour the creamy mixture into a parchment-lined baking dish, smooth the top, and cover with plastic wrap. Refrigerate for at least 3 hours until firm.

Transfer the solidified mixture to a cutting board and cut into square pieces. Set up a coating station with beaten eggs and a flour-sugar-cinnamon mix.

Heat sunflower oil in a skillet over medium heat to around 350°F. Test readiness with a wooden spoon.

Dip each piece into the flour mixture, then into the beaten eggs. Fry in batches for about 2-3 minutes on each side until golden brown.

Transfer fried pieces onto paper towels and coat immediately in cinnamon-sugar mixture. Serve warm.