What makes a good love match? Chocolate needs a grown-up playmate. He needs to stop partying with gobs of ice cream, neon cherries, rainbow sprinkles, sugary goo, and just come back to earth. Cheesecake takes advantage of him. Marshmallows are clearly a bad influence.
Saffron is smart and sensible. She’s just the bright and slightly acerbic partner that he badly needs. She puts him in his place, gets that sweetness in check, and adds color, depth, and sophistication.
Preheat the oven to 350°F. Butter and flour an 8 1/2 x 4 1/2–inch loaf pan.
In a small saucepan, bring the milk and saffron to a simmer over medium heat. Immediately remove from the heat, cover, and let stand for at least 15 minutes.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a small bowl, whisk together the saffron milk and the yogurt. In a large bowl, with an electric mixer on medium-high speed, beat the butter and granulated sugar together until fluffy, about 3 minutes. Reduce the speed to medium and add the eggs, 1 at a time, then the vanilla. Alternate adding the flour mixture and the milk mixture, beginning and ending with the flour mixture, scraping down the bowl as necessary. Fold in the chocolate.
Transfer the batter to the prepared pan and smooth the top. Sprinkle the top liberally with sanding sugar. Bake until puffed and a toothpick inserted into the center comes out with moist crumbs attached, 60 to 70 minutes. Transfer the pan to a rack and let cool for 15 minutes. Using a sharp knife, carefully loosen the cake from the edges of the pan, tip out the cake, and set it right-side up on the rack to cool completely.
The cake is best the day it’s made, but leftovers can be stored in an airtight container at room temperature for up to 3 days or frozen for up to a month.