In a medium bowl stir yeast with sugar. Stir in the milk and then add the egg yolk and melted butter.
In a large bowl whisk together the flour and salt. Pour the milk mixture over the dry ingredients and start kneading it until it pulls away from the edges of the bowl. Give the dough the shape of a ball. Sprinkle oil onto a clean bowl, place the dough and cover with plastic wrap. Let it rest for about 1 hour at room temperature until doubled in size.
While the dough rises, whisk together the butter with sugar and cinnamon for the filling. Set aside.
Preheat the oven to 400 F (200 C). Line a baking sheet with parchment paper.
On a floured surface, using a rolling pin roll the dough to a rectangle of about 18x12 inches.
Spoon the cinnamon filling over top (keep about 1 tbsp of the filling for the end), spreading evenly, leaving a clean 1/2-inch border around the edges. Sprinkle the nuts over the cinnamon filling.
Roll up the dough and using a sharp knife, cut the log in half length-wise stopping 1/2 inch from one end to keep it together.
Twist the two pieces, keeping the open layers exposed so the cut ends remain on top..Pinch the ends together and form a wreath.
Transfer it to the prepared baking sheet. Brush the wreath with the left cinnamon filling.
Bake for 20-25 minutes until golden brown. For the last 10 minutes you can reduce the oven temperature to 180 C (350 F).