From Southern California to the Pacific Northwest: My cousin, the tamale runner

Almost any Californian is likely to tell you one thing when it comes to Mexican food: Nothing beats a delicious, moist tamale.
So, yes. Let us digress – for a moment – from soybean cake.
Recently, my family and I lucked out. My cousin, Alex, and her family – all from Southern California – recently visited us in the Seattle area.
She and her husband, Raymond, were kind enough to bring a dozen chicken and pork, hand-made tamales from Diana’s. As they explained, the place enjoys a long reputation for serving up authentic, tasty Mexican food.
After my wife ate a few tamales, she said they had a smooth texture to them. She’s right: They were delicious. They weren’t dry like other tamales we’ve eaten.
So, how did my cousins succeed in this hand-delivered tamale operation?