Instructions

• Preheat the oven to 170 °C (338 °F). Place a 14 cm (5½ in) steel pastry ring on a baking sheet. Line the bottom with aluminum foil and cover the foil with baking paper; set aside.
• Divide the sugar into two equal portions.
• In a medium saucepan, combine the 400 ml milk and one portion of the sugar. Heat over medium heat, stirring occasionally, until the milk is hot and steaming but not boiling. Remove from heat if it reaches a full boil.
• In a mixing bowl, whisk together 1 egg, the remaining portion of the sugar, the 25 g fine semolina, the 12 g cornstarch, and the 5 ml vanilla extract until smooth and lump-free.
• Temper the egg mixture: while whisking constantly, slowly pour a little of the hot milk into the egg mixture to warm it. Continue adding the hot milk gradually until the egg mixture is warmed and well combined.
• Pour the tempered egg mixture back into the saucepan with the remaining milk. Return to medium heat and cook, stirring constantly, until the mixture thickens and comes to a gentle boil. Continue stirring and cook about 1 minute more to fully activate the starches, then remove from heat.
• Off the heat, stir in the 25 g butter and the zest of 1/2 lemon until the butter is fully melted and incorporated. Allow the custard to cool until it is warm to the touch (not hot).
• Transfer the warm custard to a blender and blend briefly until very smooth and free of graininess. Alternatively, whisk vigorously until smooth.
• Pour the smooth custard into the prepared pastry ring on the baking sheet, smoothing the top with a spatula.
• In a small bowl, beat the 1/2 egg with the 10 ml milk to make the egg wash. Brush the egg wash evenly over the surface of the custard.
• Bake in the preheated oven for 35–45 minutes, until the top is set and the edges are firm (the center may still have a slight wobble).
• Remove from the oven and let cool completely to room temperature before removing the ring. Serve at room temperature.