Preheat oven and liners:

Heat oven to 325°F (165°C). Insert 16 paper liners into a muffin pan.

Mix batter with chunks:

In a large bowl, combine flour, sugar, cocoa powder, and baking powder with a whisk. Pour in milk, oil, and egg; mix until just incorporated. Gently fold in chocolate chunks. Note that the batter is thin.

Bake and cool muffins:

Pour batter into the prepared liners, distributing evenly. Bake for 25 minutes, or until a toothpick inserted into the center emerges clean. Allow to cool completely on a rack.

Prepare Oreo halves:

Gently twist each Oreo to separate, ensuring the cream remains attached to one half. Halve the plain cookie halves (resulting in 16 cream halves and 16 plain halves, each plain half cut into two wedges).

Add Smartie pupil:

Place one Smartie on the cream of each Oreo half to create an eye (pupil).

Dip in melted chocolate:

Melt chocolate glaze or chocolate using a double boiler or microwave. Submerge the top of each cooled muffin into the melted chocolate, allowing excess to drip off.

Assemble face and ears:

Quickly set one Oreo cream half (with Smartie) on top of each muffin as the face, and position two plain Oreo wedges on opposite sides as ears. Repeat for all muffins. Allow to set.