Orange chocolate chip muffins

Pre-heat oven to 200°C, 400°F, Gas Mark 6. Put 12 paper cases into a muffin tin. Sift together the flour, salt, baking powder and sugar. Set to one side. In a separate bowl or jug, mix together the egg, milk, yogurt, melted butter and orange rind. Pour the wet ingredients into the flour mixture and stir lightly until just combined, adding the chocolate chunks and stirring them through gently. The mixture will be quite lumpy, though there should be no dry flour visible. Spoon the mixture into the muffin cases and bake for approximately 20 mins, or until the tops spring back when touched lightly. Cool on a wire rack.