Preheat the oven to 350 degrees F. Lightly grease an 8×4-inch loaf pan with nonstick spray. Line with parchment paper so that you have some overhanging the sides like handles and lightly grease again. Set aside.
In a medium bowl, combine 3/4 cup all-purpose flour, white whole wheat flour, cinnamon, baking soda, and kosher salt. In a separate bowl or large measuring cup, stir together the sugar and melted butter (this will help keep the butter from resolidifying). Stir in the Greek yogurt, eggs, and vanilla extract.
Add the wet ingredients to the dry ingredients, then stir together by hand with a rubber spatula, just until evenly combined—do not overmix. The batter will be very thick. Place the cinnamon chips in a small bowl. Sprinkle with remaining 1/2 tablespoon flour and toss together with your fingers (this will keep the chips from sinking to the bottom while the bread bakes). Add the coated chips to the batter, lifting the chips out with your fingers and discarding any flour that gathers at the bottom of the bowl. Fold to combine.
For the topping: Combine the sugar and cinnamon in a small bowl (I wiped the flour from the small bowl I used for the chips with a dry paper towel and reused the bowl for the topping).
Scrape the batter into the prepared baking pan and smooth the top. With a small spoon, sprinkle the topping evenly over the top. Bake for 40 to 50 minutes, until a toothpick inserted in the center comes out clean. At the 30-minute mark, lightly tent the bread with foil to prevent it from browning too quickly, then continue baking as directed. Remove the pan from the oven, uncover, and set the pan on a wire rack. Let bread cool in the pan for 15 minutes, then lift it out of the pan with the parchment paper handles and place on the rack to finish cooling completely.
Store leftovers tightly wrapped at room temperature for up to 5 days. Freeze for up to 3 months. Let thaw overnight in the refrigerator, then allow to come to room temperature before serving.
I recommend using all room-temperature ingredients so that the batter mixes more evenly and the melted butter does not solidify when it hits cold eggs or Greek yogurt.
To bake as mini loaves: Divide the batter into mini loaf pans like these, filling about two-thirds of the way to the top. Bake at 350 degrees F until a toothpick inserted in the center comes out clean. The time will vary based upon the size of your loaf pans. To be safe, I would suggest starting to check at the 28-minute mark, earlier if your pans are smaller than 2 cups.
Serving: 1slice (of 10), about 1 3/4 inch thickCalories: 196kcalCarbohydrates: 29gProtein: 4gFat: 7gSaturated Fat: 4gCholesterol: 50mgSodium: 119mgFiber: 1gSugar: 16g