Special equipment: 4 long narrow 18-inch baking pans
To make long narrow baking pans: Cut 18-inch foil pan into 4 1/2-inch by 17-inch piece. Fold long sides up twice by 7/8-inch. To close off ends, make 1-inch cuts along folds; fold center flap up and side flaps in. Spray with cooking spray. Repeat to make 3 more pans.
To assemble: Slice bread 1/4-inch thick; cut cheese to fit. Place 1 piece cheese in each sandwich. Butter outside of sandwich. Cook on hot griddle until bread is golden brown and cheese is melted, about 1 minute per side. Sprinkle with salt and serve.
To make the basic bread dough: In a small bowl, mix yeast, 1/2 teaspoon of sugar and 1/2 cup warm water. Let sit until foamy, about 5 minutes. In bowl of electric mixer fitted with a paddle, beat remaining 1 1/4 cups warm water, egg, powdered milk, 2 tablespoons sugar, salt and 1 cup flour. Beat until smooth and creamy, about 7 minutes. Add yeast mixture; beat on medium. On medium-low, beat in 3 1/2 cups flour, 1/2 cup at a time, until dough comes together (it will be sticky), about 2 minutes. Switch to dough hook. Gradually add butter; beat until dough is soft and sticks to fingers slightly, about 7 minutes. If dough is too wet, add 1/4 cup flour. On lightly floured surface, knead dough several turns into a ball. Cover dough with plastic. Let stand in warm place until it doubles in size, about 1 hour.
Preheat convection oven to 375 degrees F.
Knead dough into a smooth ball. Divide into 1/4ths. Roll each into 3/4 inch by 18 inches log; trim ends to make it 15 inches long. Fit into pans; cover with sprayed plastic wrap. Let stand in a warm place until dough reaches top of pan, 25 to 35 minutes. Place filled pans on baking sheet; brush with egg wash, sprinkle with poppy seeds and cover loosely with aluminum foil coated lightly with cooking spray. Bake 8 minutes. Remove foil; bake until lightly golden, about 4 minutes. Cool on bread rack.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.