In a large bowl, dissolve yeast in warm water. Let stand until foamy, 5 to 10 minutes.
Stir the warm milk, orange juice, sugar, ricotta cheese, orange zest, salt and egg into the yeast mixture.
Using heavy-duty electric mixer fitted with the paddle attachment and set on low speed, beat 2 cups flour into the yeast mixture until a wet dough forms. Beat in the remaining flour, 1/2 cup at a time, until a stiff dough forms.
Turn dough out onto a lightly floured surface and knead until smooth and elastic, 5 to 10 minutes, adding more flour as needed to prevent sticking.
Place the dough in a large greased bowl, turning to coat. Cover loosely with a damp cloth and let rise in a warm place until doubled, about 1 1/2 hours.
Grease a 10-inch spring form pan. Punch down the dough. Turn out onto a lightly floured surface and knead for 1 to 2 minutes.
Divide the dough into 3 equal pieces. Roll each piece into a 20-inch-long rope. Braid the ropes together.
Coil braided dough in prepared pan; tuck ends under. Cover loosely with a damp cloth and let rise in a warm place until almost doubled, 30 minutes.
Preheat oven to 425*F. Brush the dough with glaze.
Bake until the top of the cake is golden brown, 25 to 30 minutes. Turn the cake out onto a wire rack to cool slightly.
To prepare icing, in a small bowl, stir together Confectioners’ ' sugar and orange juice until smooth, Spread icing over warm cake. Serve warm.