2 packages (0.25-ounces each) active dry yeast or 5 teaspoons active dry yeast
1/2 cup water (warm for dry yeast, lukewarm for compressed)
2 cups milk, scalded
1 cup (2 sticks) butter
1 cup sugar
3/4 teaspoon salt
1 teaspoon grated {lemon peel}
2  egg yolks, beaten
8 cups flour
4 tablespoons melted butter
1  egg white, beaten
2 scant teaspoons poppy seeds
 natural Swiss cheese, thinly sliced

Sprinkle or crumble yeast into water; stir until dissolved.

Pour hot milk into large mixing bowl. Add butter in pieces, and stir until melted. Stir in sugar, salt, and lemon peel. When cooled to lukewarm, stir in egg yolks. Stir in 2 cups of the flour; beat until smooth. Add yeast mixture and enough additional flour to make a moderately firm dough; beat with a spoon until smooth. Cover and let rise in a warm place until doubled in bulk, about 2 hours.

Punch down. Divide dough into 4 parts. On a lightly floured board, roll each part into a 10-inch circle. Brush with melted butter. Cut into 8 wedges. Roll up each piece, starting at wide end. Place on a greased baking sheet, folded edge down. Allow to rise in a warm place until almost doubled in bulk, about 1 hour.

Gently brush with beaten egg white; sprinkle with poppy seeds. Bake in a hot oven (425°) for 10 minutes or until golden brown. Remove to wire rack to cool slightly. Split and fill with overlapping cheese slices.