Make pastry cream: In a medium saucepan, combine milk, cream, salt, and vanilla bean. Bring to just under a boil. In a second bowl, whisk together cornstarch and sugar, then whisk in eggs. Add a ladle of hot liquid to egg mixture, whisking constantly. Repeat twice, then whisk egg mixture into remaining milk mixture in pot.
Cook over medium heat, whisking constantly until bubbling and thick, about 2 minutes. Strain through a fine sieve, then whisk in butter. Place plastic wrap directly onto surface of cream and refrigerate until chilled, at least 2 hours and up to overnight. Whisk to loosen before using.
Assemble the trifle: Mash strawberries with 1/2 cup sugar and salt. Let stand 30 minutes.
Brush brioche with syrup and tear into large pieces. Layer bread in bottom of a 14-cup (5-by-7-inch) trifle dish or bowl. Spread 1 generous cup macerated berries over top, then 1 cup pastry cream and 1 cup whole berries. Repeat layering twice more. Refrigerate overnight.
Whip heavy cream to medium peaks with 1 tablespoon sugar and spoon over top. Garnish with fresh berries.