Preheat the oven to 180°C (350°F), conventional (top and bottom heat).
Cream the softened butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
Gently fold in the flour (and baking powder if using plain flour) until smooth—do not overmix.
Line a muffin tin with paper cases and fill each about ⅔ full with batter.
Bake for 15–20 minutes, until lightly golden. Check with a toothpick—it should come out clean.
Transfer the cupcakes to a wire rack and let them cool completely.
Mix the Greek yogurt with powdered sugar gradually until you get a thick but pipeable icing.
Transfer the icing into a piping bag (or a plastic bag with a small corner cut off).
Pipe random, curly lines onto the muffins to resemble wool.
Roll out the marzipan or fondant thinly and cut small oval shapes (these will be the lambs’ heads).
Shape small ears and attach them to the heads.
Draw the eyes and mouth using icing or a toothpick.