In a large pot, melt the butter over medium high heat and add the leeks, zucchini, a pinch of salt, and a few turns of pepper and cook, stirring, until the leeks are soft and translucent, 7-10 minutes. add the whites of the scallions and the garlic and cook for 1 more minute. stir in the flour and cook for another minute, and then add about half of the broth. cook, stirring, until the broth has thickened, and then add the other half of the broth and then cook until thickened. stir in the cream and spinach and cook until the spinach has wilted. stir in the cheese, the peas, and all but a handful of the scallion greens and then reduce the heat to low. let it simmer, stirring occasionally, while you make the biscuits.