To make yeast dough, stir 1 teaspoon sugar into warm milk and sprinkle with yeast.
Let stand 5 minutes or until the surface is frothy.
Stir gently to moisten any dry particles remaining on top.
Sift flour and salt into a large bowl.
In a medium bowl, beat eggs, remaining sugar, butter, almonds and lemon peel.
Stir in yeast mixture.
Add to flour mixture, combining to make a dough.
On a floured surface, knead dough until smooth, 5 to 10 minutes.
Cover and let rise in a warm place 30 minutes.
To make filling, blend cornstarch with a little milk, egg yolk and sugar in a medium bowl.
Put dates and remaining milk into a small saucepan; bring to a boil.
Stir milk and dates into cornstarch mixture; add butter.
Return to saucepan and bring to a boil, stirring constantly until thickened.
Cool, stirring occasionally to prevent a skin forming.
Grease a baking sheet.
On a floured surface, knead dough; roll out 1/2 inch (1 cm) thick.
Spread date mixture evenly over dough.
Roll opposite edges to meet at center; press together to flatten center.
Place on greased baking sheet; let stand 20 minutes.
Preheat oven to 400°F (205°C).
Bake stollen 1 hour or until a rich brown.
Transfer to a rack.
To make frosting, put egg white into a medium bowl; beat in powdered sugar and lemon juice.
Frost stollen while still warm.
Sprinkle with sliced almonds before frosting sets.