Preheat oven to 200°C. Grease a 12-hole muffin tray and line with paper cases.
Sift the flour, soda and spices into a large bowl. In a separate bowl, whisk together the oil, buttermilk, eggs and sugar until combined. Add to the dry ingredients and stir to combine.
Gently stir in the chocolate chips. Divide the mixture among muffin cases, then bake for 20-25 minutes until lightly browned and a skewer inserted into the centre comes out clean. Cool completely on a wire rack.
Meanwhile, place the extra 2 tbs sugar in a pan with 2 tbs water and simmer over low heat, stirring, until sugar dissolves. Brush the glaze over the muffins.
Sift icing sugar into a bowl. Add lemon juice and just enough hot water to make a thick, pipable icing. Use a piping bag or drizzle from a spoon to draw a cross on each muffin, then serve.