01 -
Set your oven to 350°F (175°C), and spray an 8x8 pan with non-stick cooking spray to avoid sticking.
02 -
Toss the flour, oats, salt, and baking soda into a big bowl, and give it a good mix.
03 -
Add the brown sugar and white sugar next, and stir until it’s all evenly mixed in.
04 -
Pour the melted butter over the dry mix, then add the vanilla extract. Stir everything until it becomes crumbly and well-blended.
05 -
Take half the crumble mixture and press it firmly into your greased pan to create an even layer.
06 -
Pop it in the oven for about 15 minutes, just enough for it to firm up a little without turning golden.
07 -
As the crust bakes, whisk your condensed milk, grated lemon zest, lemon juice, and egg yolks in a bowl until the mixture is smooth.
08 -
Once the crust is out, pour the lemon filling over the top. Then scatter the rest of the crumble mixture evenly over that.
09 -
Bake everything again for 20–22 minutes, till the topping gets lightly golden, and the lemon filling sets but isn’t wobbly.
10 -
Allow them to cool all the way down at room temp first, then refrigerate for at least 2 hours to get them firm.
11 -
To slice cleanly, chill them well or freeze for a bit. This way, the filling stays put as you cut.