Preheat your oven to 350°F (175°C). Grease a 12-cavity mini Bundt pan thoroughly with butter or nonstick baking spray, paying special attention to the ridges and center openings. Lightly flour the pan if needed, then tap out any excess flour.
In a medium mixing bowl, whisk together the all-purpose flour, granulated sugar, brown sugar, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt. Mixing these ingredients evenly helps distribute the leavening agents and spices throughout the cakes.
In a separate large bowl, whisk the pumpkin purée, oil or melted butter, eggs, vanilla extract, and milk until the mixture is smooth and evenly combined. Make sure the melted butter is not hot before adding the eggs.
Gradually add the dry ingredients to the wet ingredients. Stir gently with a spatula or whisk until the flour is just incorporated. Avoid overmixing, as this can make the finished cakes dense or tough.If the chocolate chips are large or tend to sink, toss them with a teaspoon of flour before folding them into the batter. Fold the semi-sweet chocolate chips into the pumpkin batter, distributing them evenly. Reserve a few chips for sprinkling on top if desired. The batter should be thick but easy to spoon into the prepared pan.
Spoon the batter into the prepared cavities, filling each approximately two-thirds to three-quarters full. Smooth the tops gently with the back of a spoon. Avoid overfilling, because the cakes need room to rise during baking.
Place the pan in the preheated oven and bake for 18–25 minutes, depending on the size of the cavities and your oven. The cakes are ready when a toothpick inserted into a cake comes out clean or with a few moist crumbs. Avoid testing directly through a chocolate chip, as melted chocolate may appear wet.
Remove the pan from the oven and let the cakes rest for 10–15 minutes. Carefully loosen the edges if necessary, then invert the pan onto a cooling rack. Allow the cakes to cool completely before adding any glaze or powdered sugar.
Dust the cooled cakes with powdered sugar for a simple finish, or drizzle melted chocolate over the ridges for a richer presentation. Arrange them on a serving platter and enjoy with coffee, tea, or warm apple cider.