Walnut Streusel Pie with Apricots

yeast dough

1. Grind walnuts in a food processor until finely ground.
2. Mix flour, yeast, sugar and ground walnuts together in a large bowl. Add the egg, butter and 1/2 cup milk and blend with a hand mixer until smooth.
3. Cover with handkerchief or plastic wrap; put in a warm place and let rise for 30 minutes.

topping

1. Preheat oven to 400°F.
2. Whisk vanilla custard powder with 1/3 cup milk together in small bowl until the custard powder is completely dissolved in the milk and a custard forms.
3. Bring remaining 1-1/3 cup milk to low boil with sugar. Remove from heat immediately. Pour the prepared custard slowly into the milk and sugar mixture. Whisk briskly. The mixture will thicken immediately. Pour the custard into a bowl and fold in sour cream. Let cool, stirring occasionally.
4. In the meantime, drain the apricots in a sifter or sieve.
5. Coarsely chop the walnuts for the streusel in a food processor or by hand. Add butter and knead (or pulse in food processor) until incorporated and the streusel forms large crumbles.
6. Knead the yeast dough until smooth and roll out on a floured surface. Grease a cake pan and line with yeast dough. Press the edges a little bit up the sides of the pan about 1/2 inch.
7. Spread the vanilla custard and cover with the apricots. Sprinkle the streusel over the cake. Bake for 20-25 minutes. Serve warm or cold with some powdered sugar.