Make the dough: Combine flour, sugar, yeast, and salt. Add warm milk, egg, and butter. Knead until smooth and elastic.
First rise: Cover and let rise for 1–1½ hours, until approximately doubled.
Make the pastry cream: Heat milk and cream until steaming. Whisk egg yolks, sugar, and cornstarch separately. Slowly whisk in the warm dairy, then return everything to the saucepan.
Thicken: Cook over medium heat, whisking constantly, until thick and smooth. Remove from heat and stir in butter, vanilla, and salt. Cover and cool completely.
Make cinnamon butter: Mix softened butter, brown sugar, cinnamon, and salt until smooth.
Assemble: Roll dough into a large rectangle. Spread with cinnamon butter.
Roll and cut: Roll tightly from the long side into a log. Cut into 10–12 equal rolls.
Second rise: Place in a greased baking dish, cover, and let rise for 30–45 minutes.
Bake: Bake at 350°F (175°C) for 20–30 minutes, until lightly golden and cooked through.
Frost: Let rolls cool for several minutes, then spread generously with vanilla custard.
Brûlée: Sprinkle granulated sugar evenly over the frosting. Use a kitchen torch to caramelize the sugar until golden and crisp. Let harden briefly before serving.
