1. Make the matcha custard: Whisk egg yolks, sugar, cornstarch, and sifted matcha until smooth. Heat milk until steaming, then slowly pour into egg mixture while whisking. Return to saucepan, cook over medium-low heat while whisking until thickened (2–3 minutes). Stir in vanilla. Transfer to bowl, press plastic wrap on surface, refrigerate at least 2 hours.

2. Make the dough: Whisk flour, sugar, yeast, salt, and matcha in a large bowl. Combine warm milk, melted butter, and egg in a separate bowl. Mix wet into dry until a shaggy dough forms. Knead 6–8 minutes until smooth and slightly tacky. Place in a greased bowl, cover, and let rise 1 hour until doubled.

3. Shape the rolls: Roll dough into a 12×14-inch rectangle. Spread chilled custard over dough, leaving a ½-inch border on one long edge. Roll tightly into a log and pinch the seam to seal. Cut into 9 equal pieces using a sharp knife or dental floss.

4. Second rise: Place rolls cut-side up in a greased 9×13-inch baking pan. Cover with a clean kitchen towel and let rise 30–40 minutes until noticeably puffy.

5. Bake: Preheat oven to 350°F. Bake 22–25 minutes until lightly golden and set when gently pressed in the center.

6. Add the white chocolate glaze: Melt white chocolate chips with heavy cream in a microwave-safe bowl in 20-second bursts, stirring between each, until smooth. Stir in vanilla. Drizzle generously over warm rolls.