1. Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan.
2. In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.
3. In a large bowl, combine the melted butter and sugar, mixing until smooth.
4. Add the eggs, one at a time, and mix well after each addition. Stir in the vanilla extract.
5. Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
6. Fold in the chocolate chips, followed by the milk and sour cream, mixing until smooth.
7. Pour half of the batter into the prepared cake pan, spreading evenly.
8. Drop spoonfuls of peanut butter over the batter, then top with the remaining batter.
9. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
10. Allow the cake to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Baking this cake is a sensory delight, much like those afternoons spent with my mamá, where patience and practice turned simple ingredients into culinary magic. Remember, the key is not to rush. Let each step be an act of love.