Preparation Steps

• Heat oven to 325°F (165°C). Lightly grease six 4- to 4½-inch tart pans with removable bottoms and place them on a sheet pan.
• Make the crust: Pulse the oat cookies in a food processor to fine crumbs. Add melted butter, ground ginger, and a pinch of salt; pulse just until evenly moistened. Divide the mixture among the pans and press firmly across the bottoms and up the sides. Bake 6–8 minutes until fragrant and set. Cool completely on a rack.
• Start the pudding base: In a medium bowl, whisk the egg yolks and granulated sugar until glossy and slightly lightened, then whisk in the sifted flour until smooth (it will be thick).
• Warm the dairy: In a nonreactive saucepan, combine the whole milk and sweetened condensed milk. Heat over medium until steaming with small bubbles at the edges (3–4 minutes); do not boil.
• Temper and cook: While whisking the yolk mixture constantly, slowly pour in about half of the hot milk. Scrape everything back into the saucepan and cook over medium-low heat, whisking continuously, until thickened and a few slow bubbles break the surface, 3–5 minutes.
• Finish the flavor off the heat: Remove the pan from the burner and immediately whisk in the Meyer lemon juice, lemon zest, vanilla, and a pinch of salt. Strain through a fine-mesh sieve into a clean bowl to catch any tiny curds or zest threads.
• Quick-cool: Set the bowl of pudding over an ice bath and stir for 2–3 minutes to take the edge off the heat. Spoon the warm pudding into the cooled tart shells, tapping the pan gently to level. Press a piece of plastic wrap directly onto the surface of each tart and chill until set, 2–3 hours.
• Whip the topping: Beat the cold heavy cream with the powdered sugar (and lemon zest, if using) to medium-firm peaks. Dollop or swirl over the chilled tarts. Garnish with extra zest or a paper-thin Meyer lemon slice and serve cold.