Make the pastry cream: Put milk and coconut in a medium saucepan over medium-high heat. Scrape seeds from vanilla bean and add both seeds and bean to saucepan. Bring mixture to a gentle simmer, stirring occasionally.
In a medium bowl, whisk together eggs, sugar, and flour. While whisking, drizzle about 1/3 of the hot milk mixture into egg mixture, then slowly whisk egg-milk mixture back into saucepan. Cook over medium-high heat, whisking, until pastry cream thickens and begins to bubble, 4 to 5 minutes. Remove from heat, stir in butter, and discard vanilla bean.
Spoon hot pastry cream into a bowl and set in a larger bowl of ice and cold water, stirring occasionally, until cooled to room temperature. Cover with plastic wrap, pressing it directly onto surface (to prevent a skin from forming) and chill until cold, at least 3 hours.
Fill the pies: Carefully remove baked shells from brioche molds. Spoon pastry cream into shells, filling each a little more than halfway. With an electric mixer, whip cream with sugar and vanilla until it holds stiff peaks. Fill a pastry bag fitted with a large star tip (no. 6) with whipped cream and pipe a double layer of cream onto each pie, or simply spoon it on (use all the cream--the pies should look like beehive hairdos).
Garnish the pies: With a vegetable peeler, scrape wide curls or shavings from the chunk of white chocolate. Sprinkle curls or shavings over pies, dividing evenly, and top with toasted coconut. Serve immediately.
Note: Nutritional analysis is per mini pie.