vegetarianInfuse the milk
Pour about three quarters of the whole milk into a medium saucepan and keep the rest cold for later. Add the cinnamon stick and the lemon peel, then warm everything over medium heat until the milk is steaming and you see tiny bubbles around the edge, about 5 minutes. Take the pan off the heat, cover loosely, and let the flavors steep for 10 minutes.
Whisk the base
In a large bowl, whisk the reserved cold milk with the cornstarch until completely smooth. Add the sugar, the egg yolks, and the salt, and whisk again until you have a pale, lump-free mixture.
Cook the custard
Fish out and discard the cinnamon stick and lemon peel from the infused milk. Slowly pour the warm infused milk into the bowl while whisking, then return the mixture to the saucepan. Cook over medium-low heat, stirring constantly and scraping the bottom and corners, until it turns very thick, glossy, and starts to burp a few slow bubbles, about 6 to 8 minutes. Take it off the heat and stir in the unsalted butter until fully melted and smooth.
Set and chill
Spread the hot custard into a parchment-lined square dish or small baking pan, smoothing the top into an even layer about 1 inch thick. Press a piece of parchment or plastic wrap directly onto the surface so it does not form a skin. Let it cool on the counter for 15 minutes, then refrigerate until very firm, at least 3 hours.
Cut the custard
Lift the chilled slab out of the dish and place it on a board. Trim the edges if you want neat pieces, then cut it into 8 rectangles or 16 smaller squares, depending on how you want to serve it.
Coat the pieces
Put the all-purpose flour in one shallow bowl. In a second shallow bowl, beat the eggs until smooth. Dredge each custard piece lightly in flour, tapping off the excess, then dip it in egg so it is fully coated.
Fry until golden
Pour the light olive oil into a deep skillet or saucepan so you have a generous shallow layer, and heat it over medium heat until it reaches 350° F. Fry the coated custard pieces in small batches, turning carefully, until both sides are lightly golden and crisp, about 1 to 2 minutes per side. Transfer them to a rack or paper towels to drain briefly.
Mix cinnamon sugar
While the pieces are frying, stir the remaining sugar together with the ground cinnamon in a shallow bowl or plate until evenly blended.
Finish and serve
While the leche frita is still warm, roll or sprinkle each piece with the cinnamon sugar so it sticks well. Serve warm or at room temperature, with the crisp outside and creamy center at their best.
