Rhubarb streusel muffins

At last, we have proper rhubarb harvest. Not epic, but enough, and thick enough. So I got excited and this was what I decided to make... It maybe wasn't the most important thing to do that day, but I felt like it was the thing to do... It's crazy how a little kid makes you prioritize... It's essentially an amalgamation of two recipes: here and here.

(makes 12)

For the muffins:
1 1/2 cups flour (approx 50:50 wholewheat or spelt and plain)
1/2 tsp bicarbonate of soda
1/2 tsp salt
3/4 cup brown sugar
1/2 cup veg oil
1 egg
1/2 cup runny yoghurt (dilute a little with water if thick)
1 tsp vanilla essence
1/2 cup chopped toasted walnuts
1 1/2 cups chopped rhubarb (approx 1 cm dice)

For the streusel topping:
1/2 cup flour (mix as above)
1/4 cup brown sugar
1/2 tsp cinnamon
1/4 cup chopped walnuts
3 tbsp melted butter

Heat oven to 165C and line a muffin tin. Mix flour, bicarb and salt with a fork in a large bowl. Beat sugar, oil, egg, yoghurt and vanilla together with a fork in another bowl. Add wet to dry and mix until just combined, adding the chopped walnuts and rhubarb with the last few strokes. Dollop into muffin liners, leaving a little space for topping. To make the streusel, mix the flour, sugar and cinnamon in a bowl with a fork, then add the melted butter and stir until lumpy, then add the walnuts. Distribute evenly over the muffins. Bake for approx. 30 min, until lightly browned on top and a skewer comes out clean.