Set a rack in the centre of the oven, and preheat the oven to 350F. Grease a standard-sized (about 9 by 5 inches/23 by 13 cm) loaf pan with cooking spray or butter.
In a small bowl, microwave the butter until just melted. (Take care to do this on medium power and in short bursts; if the heat is too high, butter will sometimes splatter or explode. Or, alternatively, put the butter in a heatproof bowl and melt in the preheated oven.) Set aside to cool slightly.
In a large bowl, whisk together the flour, sugar, baking soda, and salt. Add the chocolate chips and crystallized ginger and whisk well to combine. Set aside.
In a medium bowl, lightly beat the eggs with a fork. Add the mashed banana, yogurt, melted butter, and vanilla and stir to mix well. (The same fork works fine for this.) Pour the banana mixture into the dry ingredients, and stir gently with a rubber spatula, scraping down the sides as needed, until just combined. Do not overmix. The batter will be thick and somewhat lumpy, but there should be no unincorporated flour. Scrape the batter into the prepared pan, and smooth the top.
Bake until the loaf is a deep shade of golden brown and a toothpick inserted into the centre comes out clean, 50 minutes to 1 hour. If the loaf seems to be browning too quickly, tent with aluminum foil.
Cool the loaf in the pan on a wire rack for 5 minutes. Then tip it out onto the rack, and let it cool completely before slicing unless you absolutely can't help yourself, in which case, dig in.
Note: Fully cooled, this bread freezes beautifully. And it tastes delicious cold, straight from the freezer. To protect it from frost, wrap it in plastic wrap and then again in aluminum foil.