In a small bowl, combine the cream cheese, instant coffee, powdered sugar, and ground chocolate or cocoa powder.

Mix well until smooth and set aside.

In a large bowl, whisk together the flour, baking powder, baking soda, and salt.

In a separate bowl, whisk the eggs with sour cream, sugar, and vanilla extract.

Create a well in the center of the dry ingredients and pour in the egg and sour cream mixture.

Stir for approximately 10 seconds, until just combined. Do not overmix; the dough will be thick.

Grease a 12-cup muffin tin.

Spoon batter into the prepared muffin cups, filling them about one-third full.

Drop a heaping teaspoon of the cream cheese mixture into the center of each muffin cup, being careful not to touch the edges of the pan.

Top each muffin with the remaining batter, ensuring the cream cheese filling is completely covered.

Preheat oven to 375 degrees Fahrenheit (190 degrees Celsius).

Place the muffin tin on the center rack of the preheated oven.

Bake for 18 to 20 minutes, or until the muffins are golden brown and a toothpick inserted into the center comes out clean.

Let the muffins cool in the pan for a few minutes before transferring them to a wire rack to cool completely.