Prep the pan and oven. Heat the oven to 325°F (165°C). Grease a 9x5-inch loaf pan or a 10-cup bundt/tube pan. Line the loaf pan with a parchment sling for easy removal, and lightly dust with cocoa.

Melt the chocolate. Gently melt the semisweet chocolate in the microwave in short bursts or over a double boiler. Stir until smooth and let it cool to lukewarm.

Whisk the dry ingredients. In a bowl, whisk the flour, cocoa, baking powder, baking soda, and salt until well combined. This prevents clumps and ensures even mixing later.

Cream butter and sugars. In a large bowl, beat the butter, granulated sugar, and brown sugar on medium-high until light and fluffy, about 3 minutes. The mixture should look pale and airy.

Add the eggs. Beat in the eggs one at a time, mixing well after each. Scrape the bowl so everything stays smooth. Stir in the vanilla.

Add the melted chocolate. Pour in the cooled melted chocolate and mix just until fully blended. The batter will deepen in color and smell amazing.

Alternate dry ingredients with dairy. On low speed, add one-third of the dry mixture, then half the sour cream and milk. Repeat, ending with the dry mixture. Mix just until no dry streaks remain. Do not overmix.

Fold in chips (optional). If using chocolate chips, toss them in a teaspoon of flour, then fold gently into the batter to help prevent sinking.

Fill the pan and smooth. Scrape the batter into the prepared pan and smooth the top. For a classic pound cake crack, run a buttered knife down the center of the loaf.

Bake. Bake 60–75 minutes for a loaf pan, or 50–65 minutes for a bundt, until a skewer comes out with a few moist crumbs. If the top is browning too fast, tent loosely with foil.

Cool properly. Cool in the pan for 15 minutes, then turn onto a wire rack. Let it cool completely before slicing. This sets the crumb and keeps slices clean.