Step 1

Preheat oven to 160 degrees celsius (fan-forced.

Step 2

Grease and line a 18cm x 28cm slice tray with baking paper, allowing the edges to overhang.

Step 3

In a large bowl, whisk together the plain flour, rolled oats, salt and bi-carbonate of soda.

Step 4

Stir in the raw sugar and brown sugar and mix until smooth.

Step 5

Stir vanilla extract into melted butter and pour mixture over dry ingredients.

Step 6

Stir mixture until well combined.

Step 7

Press just over half of the crumble mixture into the base of the prepared tin and use the back of a spoon to smooth the mixture into an even layer. Bake in the preheated oven for 15 minutes, until golden.

Step 8

Remove from oven and put aside (leave the oven turned on).

Step 9

Sprinkle the blueberries over the cooked crumble base.

Step 10

In a bowl, whisk together sweetened condensed milk, lemon zest, lemon juice, egg yolks and lemon extract (optional) until smooth and slightly thickened.

Step 11

Pour the lemon mixture over the blueberries and spread into an even layer.

Step 12

Sprinkle the remaining crumble mixture over the top of the lemon filling and blueberries.

Step 13

Bake in oven for 23 - 26 minutes or until lightly golden.

Step 14

Remove from oven and allow to cool.

Step 15

Cover and refrigerate for at least 2 hours (preferably overnight) then take it out and cut into squares. Store in airtight container in the refrigerator for up to 1 week.

Step 16

Preheat oven to 160 degrees celsius (fan-forced).Grease and line an 18cm x 28cm slice tray with baking paper, allowing the edges to overhang.

Step 17

Melt the butter and vanilla extract in the Thermomix bowl for 3 minutes, Speed 2, 80 degrees.

Step 18

Add the plain flour, rolled oats, salt, bi-carbonate of soda, brown sugar and raw sugar. Mix for 20 seconds on Reverse, Speed Scrape down the sides. Mix for a further 20 seconds on Reverse, Speed 2.

Step 19

Press just over half of the crumble mixture into the base of the prepared tin and use the back of a spoon to smooth the mixture into an even layer. Bake in the preheated oven for 15 minutes, until golden.

Step 20

Remove from oven and put aside (leave the oven turned on.

Step 21

Place the zest of 1 lemon into the Thermomix bowl. Grate for 20 seconds, Speed Scrape the sides of the bowl. Repeat until you have a very finely grated zest.

Step 22

Add the sweetened condensed milk, lemon juice, egg yolks and lemon extract (optional) and mix for 30 seconds, Speed Scrape the sides of the bowl and mix for a further 30 seconds, Speed 4.

Step 23

Sprinkle the blueberries over the cooked crumble base. Pour lemon mixture over the blueberries and spread into an even layer.

Step 24

Sprinkle the remaining crumble mixture over the top of the lemon and blueberries.

Step 25

Bake in oven for 23 - 26 minutes or until lightly golden. Remove from oven and allow to cool.

Step 26

Cover and refrigerate for at least 2 hours (preferably overnight) then take it out and cut into squares. Store in airtight container in the refrigerator for up to 1 week.