I used Nigella Lawson's recipe for chocolate chip muffins as a guideline, as it uses vegetable oil rather than butter. Here's one online version of the recipe. Foolishly, I left out the chocolate chips, and lived to regret it. I also used SR flour instead of plain flour + baking powder, and used 200g flour and 50g ground almonds. The only other change was to add a few drops of almond extract to the liquid ingredients.
When cool this was crumbled evenly over the muffin batter before baking.
The recipe worked quite well, considering muffins aren't one of my strong points, although my efforts not to overmix left a few floury patches in the muffins. I just can't get it completely right!
Because of the butter in the streusel topping, I can't really claim these are low in saturated fat, but they're not as bad as if I'd used butter in the muffin batter too! The mildness of the chocolate flavour allowed the almond flavour to come through too.