Melt 45g of butter using a double boiler. Place a small pot with some water on low heat, then set a heatproof bowl containing the butter over the pot. Stir continuously until the butter is fully melted.

Add 90g milk and 50g granulated sugar to the melted butter. Stir well until the sugar dissolves completely.

Crack 1 egg into the butter mixture and whisk thoroughly until smooth and well combined.

In a separate bowl, sift together 80g cake flour, 15g cocoa powder, 15g cornstarch, 15g milk powder, and 5g baking powder. Gradually add this mixture into the wet ingredients, stirring gently after each addition.

Note: Sifting ensures the dry ingredients are fine and prevents lumps, resulting in a smoother batter.

Whisk the dry ingredients into the wet mixture until fully incorporated and smooth. Be careful not to overmix, as overmixing can develop the gluten and result in dense muffins.

Spoon the batter into a piping bag and pipe it into mini muffin molds, filling each about 80% full. Sprinkle 5-6 chocolate chips on top of each muffin.

Preheat your oven to 170°C (340°F). Place the filled molds on the middle rack and bake for 20-22 minutes. If the tops brown too quickly, cover with aluminum foil.

Once baked, remove the muffins from the oven and let them cool completely before serving. But if you're anything like me, waiting might be impossible—I can never resist grabbing one while they're still warm and enjoying that melty chocolate goodness right away!