In a mixing bowl sift 2 cups of flour and mix it with active dry yeast. Cut 2 sticks of cold butter in small pieces and add it to the flour. You can use a pastry cutter or your hands to mix butter with the flour and yeast until the crumbles are pea size.
In a separate bowl mix 1 cup of sour cream, sugar, 2 egg yolks and vanilla. Add it to the dry ingredients, and mix it again.
Add the rest of the flour and knead the dough until it is smooth and doesn’t stick to your hands.
Divide the dough into 6 even pieces and wrap with plastic wrap. Refrigerate it for an hour.
Preheat the oven to 350°F, line a baking sheet with a parchment paper and set aside.
When the dough is ready, take one ball and roll it to about 2-3 mm thick. Using a pizza cutter cut it in 12 equal pieces.
Spread 1/3 cup of apricot jam over the dough and sprinkle 1/3 cup of finely chopped walnuts. Using a pizza cutter cut it in 12 equal pieces. Roll every piece into a rugelach.
Bake at 350°F for 18-20 min, until they have a beautiful golden color.
When baked, take them out of the oven and let sit on the baking sheet for about 10 minutes before transferring to a wire rack.
As an option, you can dust them with powdered sugar over the top.