To prepare walnut potica, combine flour and yeast in a bowl while heating milk, butter, sugar and salt in a saucepan. Add the wet ingredients to the dry, add eggs, and let the mixture rise. Mix walnuts, sugar, butter, honey, egg, milk and vanilla for the filling. Shape dough into loaves, and fill with walnut mixture. Bake in a 325-degree oven for 45 to 50 minutes.
Combine 1 cup of flour with one package of active dry yeast. Heat 1/3 cup of milk, 1/4 cup of butter, 2 tablespoons of sugar and 1/2 teaspoon of salt until butter is nearly melted. Add the milk mixture to the flour, then add two eggs. Beat with an electric mixture on low for 30 seconds, then on high speed for 3 minutes. Knead this mixture to make a soft dough, adding in just enough flour, and shape into a ball.
Put dough into a greased bowl, turning to coat. After about an hour in a warm location, the dough should double in size. While the dough is rising, prepare the filling by adding 3 cups ground walnuts, 3/4 cup sugar, 1/4 cup butter, 1/4 cup honey, one slightly beaten egg, 3 tablespoons milk and 1/2 teaspoon vanilla. Punch the dough down, cover, and let sit for 10 minutes.
Lightly grease two loaf pans. On a floured surface, roll dough into a 15-inch square. Let sit for 10 minutes, then roll dough into a rectangle shape, approximately 30 inches by 20 inches. Cut dough in half, lengthwise, and add filling. Roll up each loaf, cover and let rise about one hour. While baking, cover each loaf with foil during the last 15 minutes to prevent burning.