For dough: Dissolve yeast in water and let stand until foamy, about 10 minutes.
Add olive oil, salt and enough of the flour so dough can be handled easily.
Turn out onto generously floured surface and knead until dough is shiny and elastic.
Place in greased bowl, turning to coat entire surface.
Cover with towel and let rise until dough has doubled, about 1 hour.
For filling: Remove sausage from casings and crumble meat into skillet.
Saute over medium-high heat until no pink remains.
Drain well and transfer to large mixing bowl.
Wipe out skillet.
Using same skillet, cook pine nuts in olive oil until golden.
Add garlic and cook briefly.
Add to sausage along with spinach, ricotta and egg and mix well.
Season to taste with salt and pepper.
Punch dough down and divide in half.
Roll each half into 15 x 15 inch square.
Cut into 5-inch squares.
Place about 2 rounded tablespoons of filling on each square.
Gather edges of dough around filling and press together to seal.
Place buns pinched side down on ungreased baking sheet.
Let stand in warm place for about 15 minutes.
Preheat oven to 425°F.
Brush buns with egg mixture.
Bake until golden, about 25 to 30 minutes.
Let cool on wire racks.