Preheat the Oven. Preheat your oven to 180°C (350°F) and line a muffin tin with paper cases or lightly grease it to prevent sticking.
Combine Dry Ingredients. In a large bowl, mix together the self-raising flour, oats, sugar, and bicarbonate of soda. This dry mixture will form the base of your muffins.
200 g self-rising flour, 50 g oats, 1 tsp bicarbonate of soda, 80 g sugar
Mix Wet Ingredients. In another bowl, combine the melted butter, milk, eggs, and white vinegar (or lemon juice). Add the mashed bananas and stir until well mixed. The vinegar or lemon juice helps activate the bicarbonate of soda, giving the muffins a nice rise.
100 g butter, melted, 100 ml milk, 2 eggs, ½ tbsp white vinegar or lemon juice, 1 bananas, mashed
Combine Everything. Pour the wet ingredients into the dry ingredients and gently mix until just combined. Be careful not to overmix, as this can make the muffins dense.
Add the Goodies. Fold in the frozen raspberries and white chocolate chips (if using). The raspberries will add a lovely tartness, while the chocolate provides a sweet contrast.
½ cup frozen raspberries, 1/2 cup white chocolate chips
Fill the Muffin Tin. Spoon the batter into the prepared muffin tin, filling each case about two-thirds full. This allows room for the muffins to rise without overflowing.
Bake. Bake in the preheated oven for about 20-25 minutes, or until the muffins are golden brown and a toothpick inserted into the center comes out clean. Keep an eye on them towards the end of the baking time to avoid overcooking!
Cool and Enjoy! Once baked, remove the muffins from the oven and let them cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely. They’re delicious warm or at room temperature.