Heat butter and milk over low on stovetop until butter has melted. Cool to lukewarm.
In a large bowl, dissolve the yeast in the warm water and beat in the egg yolk. Blend in the cooled milk mixture.
Sift in the flour, salt and sugar. Beat until the mixture is smooth and creamy.
Cover bowl and refrigerate overnight.
FOR THE FILLING:
The next day, blend together walnuts, cinnamon, sugar, dates and milk for the filling in a saucepan over medium-low heat. Stir until mixture thickens. Let cool.
Beat egg whites until stiff and slowly add in the 1 cup of sugar. Fold into the cooled walnut mixture.
Divide dough into two equal pieces and dust each with flour. Roll out (one at a time) to make an 18-inch circle. Pour half of the walnut filling onto the dough and spread out over the dough and roll up jelly-roll fashion.
Carefully place into a bundt pan that has been sprayed with non-stick cooking spray.
Repeat with the second half and carefully place that half on the other side of the pan, overlapping the first half.
Place on stovetop and let rise for 30 minutes while preheating the oven to 350 degrees.
Bake for 45 minutes.
Cool in pan for 15 minutes and then invert to a cake plate.
FOR THE GLAZE:
Place the powdered sugar in a medium-size bowl.
Add the heavy cream a tablespoon at a time until you reach the consistency you’d like your icing or drizzle to be.
Add the flavor extract of your choice. Mix well.
Drizzle the glaze over the cake.
Serve fresh for best results or reheat slices in microwave for 30 seconds prior to serving to retain moistness.