Preheat the oven to 350°F (180°C). Line a 9x5-inch loaf pan with parchment paper, leaving some overhang for easy removal. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, combine the sugar and eggs. Beat with an electric mixer for about 3 minutes, until pale in color.
Add the softened butter to the bowl and beat for an additional 3-4 minutes, until smooth and creamy.
Beat in the cinnamon and vanilla extract or vanilla bean paste.
Stir in the buttermilk and Greek yogurt (or sour cream).
Gradually add the flour mixture to the wet ingredients and mix until just combined with a spatula.
Gently fold in the chocolate chips. Mix until just combined; avoid overmixing.
Pour the batter into the prepared loaf pan and smooth the top.
Sprinkle additional chocolate chips over the batter.
Bake for 50-60 minutes or until a toothpick inserted into the center comes out clean.
Remove from the oven and let cool in the pan for 10 minutes.
Transfer the loaf to a wire rack and let cool completely before slicing and serving.