(Almost Vegetarian): White Lasagne with Parmigiano Besciamella, Spinach & Ricotta

Okay, we are starting this thing where Saturday night is designated, "Vegetarian Night". So far we've had this, an Indian Feast (coming soon), and this weekend, the Vegetable Upside-down Cake from the Enchanted Broccoli Forest. But now, here's lasagna. Originally, it was just sauce, noodles, and Parmesan. This sounds great but why not add a …