Preheat your oven to 400°F (200°C).

Melt the 1/2 cup (1 stick) of unsalted butter in a microwave-safe bowl or small saucepan. Pour the melted butter directly into a 9x9 inch baking dish, ensuring the bottom is evenly coated. Set aside.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

In a separate small bowl or measuring cup, combine the cold whole milk and vanilla extract.

Pour the wet ingredients into the dry ingredients. Mix with a spatula until just combined and a shaggy dough forms. Be careful not to overmix; a few lumps are fine.

Gently fold in the semi-sweet chocolate chips until they are evenly distributed throughout the dough.

Carefully transfer the biscuit dough into the prepared baking dish, on top of the melted butter. Use your spatula to gently spread the dough evenly across the dish, making sure it touches all edges. Do not press down too firmly.

Using a knife or bench scraper, gently score the top of the dough into 9 equal squares (3 rows by 3 rows). Do not cut all the way through the dough to the bottom of the dish; this is just to guide the biscuits when they bake and make them easier to pull apart.

Bake for 22-28 minutes, or until the tops are golden brown and the biscuits are puffed up and cooked through. The butter will bubble up around the biscuits, creating a rich, crispy bottom.

Remove from the oven and let cool in the pan for at least 10-15 minutes before serving. This allows the biscuits to set and absorb some of that delicious butter. Serve warm.