In an electric mixer, beat the butter and sugar until pale and creamy.
Add eggs one for one until incorporated.
In another mixing bowl, add all your dry ingredients except the berries.
Add the margarine and sugar mixture to the dry ingredients and add the yogurt little by little while mixing, alternating with the milk and vanilla essence– just until incorporated.
Add your berries by folding it into the batter.
Fill muffin holders ¾ with batter, and bake for 25 minutes at 180 degrees Celsius, or until golden brown.