I decided to experiment with muffins.  I decided upon a vanilla muffin with a chocolate centre to see how that would work.

They certainly look good, and have a gooey centre, though they are just a little too gooey to be able to peel from the paper.  A spoon was necessary to eat the base, as the chocolate seeped into the base.  I think that means that I should make the chocolate centre slightly firmer next time.

I think that using a dark chocolate rather than a milk chocolate for the centre may actually be better, since it has a firmer consistency so will firm up in the fridge just that little bit better.  

So, not entirely successful, but certainly worth a try.

Ingredients:

• 350 grams plain flour
• 170 grams granulated sugar
• 1 Tablespoon baking powder
• 1/2 teaspoon salt
• 113 grams unsalted butter, melted
• 240 ml milk, room temperature
• 2 large eggs, room temperature, lightly beaten
• 1 Tablespoon pure vanilla extract
• some dark chocolate sprinkles
• 4 ounces milk chocolate, chopped
• 1/4 cup heavy cream
• 1/2 tablespoon unsalted butter

1. Preheat the oven to 200c/180 c Fan. line a 12 hole muffin tin with paper cups
2. For the gooey center: Combine the milk chocolate, heavy cream and butter in a small saucepan and heat over low heat, whisking until the chocolate is completely melted and smooth. Pour this mixture into a small glass baking dish and chill until set, about 1 hour. Scoop and roll into 12 small balls and place on a small parchment-lined plate or tray. Wrap and chill for at least 30 minutes up to overnight. 
3.  In a large bowl, add the flour, sugar, baking powder, and salt. With a whisk, mix the dry ingredients until well-blended.
4. In a small bowl or beaker add the melted butter, milk, beaten eggs and vanilla. Stir with a fork until the liquid is well mixed. Make a well in the center of the dry ingredients. Add the wet ingredients (liquid) to the center of the well.
5. Add some mixture into each muffin cup, about one third full.
6. Place one chocolate ball on top of that mixture.
7. Using the remaining mixture cover the chocolate balls completely, until an equal amount of the mixture is in each muffin cup
8. Distribute the dark chocolate sprinkles over the top of each muffin
9. Bake the muffins for 15 to 20 minutes, or until they have risen and are light golden brown of the edges. 
10. Remove the muffins from the oven, cool for 10 minutes in the muffin pan. 
11. Remove muffins from pan and finish cooling on a wire baking rack.