In a saucepan bring the Whole Milk to a gentle simmer with a Cinnamon Stick, a strip of Lemon Peel and half the Sugar, stirring occasionally to dissolve the sugar and infuse the milk with flavor; remove from heat, cover and let steep for 10–15 minutes, then strain and reserve the infused milk.
Whisk together the Cornstarch with a little of the reserved infused milk to form a smooth slurry, then stir in the remaining Sugar until combined.
Return the strained milk to medium heat and slowly whisk in the cornstarch mixture; cook, stirring constantly, until the mixture becomes very thick and glossy.
Temper the beaten Egg Yolks by whisking in a few tablespoons of the hot milk mixture, then quickly stir the warmed yolks back into the pan; continue cooking another minute while stirring, then remove from heat.
Stir in the Unsalted Butter and a pinch of Salt until the butter is melted and fully incorporated; transfer the thick custard to a lightly buttered shallow pan, smooth the top, cover with plastic wrap touching the surface, and chill until very firm (at least 2 hours or overnight).
Turn the set custard onto a cutting board and cut into rectangles or squares. Place the pieces on a tray and prepare three bowls: one with All-Purpose Flour, one with beaten Eggs, and another with more flour for a final dusting.
Dredge each custard piece first in flour, then dip in the beaten eggs, and give a light second dusting of flour to ensure a crisp crust; handle gently to keep the pieces intact.
Heat enough Light Olive Oil in a heavy frying pan to shallow-fry (about 1/4–1/2 inch deep) until shimmering. Fry the coated custard pieces in batches over medium heat until golden brown on both sides, about 1–2 minutes per side. Drain on paper towels.
Mix remaining Sugar with Ground Cinnamon and sprinkle generously over the warm leche frita before serving. Enjoy while slightly warm so the center remains creamy and the exterior stays crisp.
