Set oven to broiler setting. Place thick slice of milk bread on baking sheet. Spread salted butter over one side of bread. Sprinkle 2tsp cinnamon sugar over buttered bread. Place until broiler for 50-70 seconds until the sugar has started to caramelize.
Pulse granulated sugar and cinnamon together until sugar is fine. Alternately, simply whisk together sugar and cinnamon.
For a super rich and decadent milk toast: spread salted butter over bread, drizzle sweetened condensed milk over butter, then sprinkle cinnamon sugar on top. Place under broiler for 50-70 seconds until sugar has melted.