In a medium bowl combine flour, yeast and baking powder.
In a large bowl whisk together egg, warm milk, sugar and melted butter. Gradually stir in flour and yeast mixture and knead until the dough is smooth and not sticky. Cover the bowl with a plastic wrap and place it in a warm place to rise for 30-40 minutes.
Meanwhile, in a medium bowl mix together walnuts and apricot preserves.
Preheat the oven to 355 F.
Line 13x9-inch baking pan with a parchment paper. Divide the dough into 3 equal parts.
Lightly dust a working surface with a flour and roll out the first piece of dough to be the size of your baking pan. I used a ruler for convenience.
Transfer first layer of dough into the baking pan and spread half of the apricot-walnut mixture on top. Repeat with the remaining 2 layers of dough.
Pierce the top layer with a fork 10-15 times.
Bake the cake for 25-30 minutes until top is golden brown.
Remove cake from the oven and let it cool.
In a small bowl combine butter and chocolate and microwave in 10-15 seconds intervals until melted. Give it a stir and evenly spread the chocolate on top of the cake.
Chill for an hour or until chocolate is set.