Rhubarb crumble muffins

Crumbles are often considered a fail safe homemade dessert. But I've never actually made it, NOT ONCE! So, I thought despite never made a crumble OR a muffin EVER, I've decided to combine the two and make my life difficult by combining the two!

Ingredients (makes 12)

• 250g rhubarb (diced)
• 250g caster sugar
• 2 tbsps vegetable oil
• 120ml milk (full fat/semi-skimmed)
• 2 tsps vanilla extract
• 1 large egg
• 200g self raising flour
• 1 tsp baking powder
• 75g unsalted butter
• 75g muscovado sugar 
• 75g plain flour
• 35g porridge oat
• 1 tsp cinnamon

1. Pre-heat oven to 220 degrees C/200 fan
2. Place muffin case into the 12 hole muffin tin
3. Mix muscovado sugar, plain flour cinnamon and porridge oat together
4. Rub in sugar into the dry ingredients until it resembles breadcrumb, set it aside and start preparing the filling
5. Cut rhubarb along the length and cut it into 1.5-2cm cubes
6. Add caster sugar to rhubarb and mix
7. Add vegetable oil, milk, vanilla extract and egg together and mix well
8. Sift and add self raising flour and baking powder to wet ingredients and mix well
9. Divid batter into the 12 muffin cases, fill 3/4 of the way
10. Place crumble on the muffin batter
11. Bake for 15-20 minutes, make sure to rotate the muffin tin if one side of the oven bakes hotter than the other side