Cornish Hens with Aromatic Green Sauce

This richly fragrant, savory dish has its origins in the Mexican mole verde (an herbal green sauce) and pollo en pipián (chicken in squash or pumpkin-seed sauce). I have combined the two to my taste to make a dish that is at once spicy and herbal, leafy and lemony—and quick to prepare. If you don’t fancy heat, eliminate the jalapeño; if you’re a passionate pepper fan, use a whole instead of half.