Chocolate Chocolate-Chip Muffins

Been wanting to bake this week and have been searching for blueberries to bake some blueberries muffins but alas, couldn't find it at any stores near me and I'm too lazy to pop over to NTUC to get the blueberries.
Therefore, wanted to make do with the chocolate chip muffins till I thought of, why not do a Chocolate Choc Chips Muffins?
I searched for the recipe from Tested & Tasted and found this recipe from Angel of Cook.Love.Bake.
I modified the recipe a bit because I'm using self-raising flour instead of plain flour with baking soda and powder, changed vanilla extract to vanilla essence and changed the vegetable oil to butter also.

Recipe I used:

Ingredients: (makes 12 muffins)

260g self raising flour

2 tbsp best quality cocoa powder

170g caster sugar

150g chocolate chips (save 1/4 of the chips for sprinkling)

250ml milk

90ml melted butter

1 large egg

1 1/2 tsp vanilla essence

Method:

1) Preheat the oven to 200 deg C.

2) Put the flour,cocoa, sugar, and 3/4 of the chocolate chips into a large bowl and mix well.

3) Pour all the liquid ingredients into a measuring jug and mix well.

4) Add the wet ingredients to the dry ingredients and mix together with slow and gentle strokes. Stop stirring once the last traces of flour disappear. Do not over mix. A lumpy batter will ensure the muffins stay moist and fluffy.

5) Spoon the batter into paper muffin cases.

6) Sprinkle the remaining 1/4 chocolate chips on top and bake for 20 minutes or until the muffins are dark, risen and springy.