Preheat oven to 350°F (175°C). Grease and fully line a 9x5-inch loaf pan with parchment paper.

Make the streusel. In a medium bowl, combine the flour, granulated sugar, brown sugar, optional sanding sugar, and salt. Add the cold butter and vanilla bean paste. Work together until crumbly with a mix of small crumbs and larger clusters. Fold in the mini chocolate chips. Refrigerate while preparing the batter.

In a large bowl, whisk together the granulated sugar, oil, yogurt, milk, vanilla bean paste, and apple cider vinegar until smooth.

Add the flour, cornstarch, baking powder, baking soda, salt, and nutmeg. Whisk just until combined and no dry streaks remain.

Fold in the mini chocolate chips just until evenly distributed.

Transfer the batter to the prepared loaf pan and smooth the top. The batter should fill the pan just over halfway full.

Sprinkle the chilled streusel evenly over the batter, leaving some larger clusters intact.

Sprinkle the top lightly and evenly with coarse sanding sugar just before baking.

Bake for 45-55 minutes. It may look slightly undone in the center; that is okay. A few minutes after baking, sprinkle with Maldon flaky sea salt.

Cool in the pan for 25-30 minutes, then transfer the loaf to a wire rack.

Whisk together the powdered sugar, milk, vanilla bean paste, and salt until smooth and pourable. Drizzle the glaze evenly over the still-warm loaf.

Allow the loaf to cool completely at room temperature.

Chill for about 30 minutes, or until the glaze and center feel set enough for clean slices. If you want to serve it warmer, let it set on the counter instead.