Oatmeal Lemon Slice (Bars)

[mific]

I needed to use up some aging lemons, and some rolled oats. Adapted this recipe and it's a winner!
Makes about 16 squares. GF, low GI, and can be dairy free & vegan.

Ingredients:
Oatmeal crumble:
1/2 cup butter, melted and cooled to lukewarm
1 cup rolled oats
1 cup oat flour (can make it from more rolled oats, in a blender)
1 tablespoon psyllium powder
1 teaspoon baking powder
1/2 teaspoon salt
1/2 cup dried coconut (shredded or flaked)
3/4 cup golden erythritol/brown sugar
1/2 cup chopped walnuts
1 teaspoon vanilla extract
2 tablespoons cream or milk

Lemon Filling:
14 ounce (~350 grams) can of keto sweetened condensed milk (made from coconut milk) - or use ordinary condensed milk, or sub as in Notes below.
2 tablespoons cornflour
1/2 cup (120 grams) freshly squeezed lemon juice
grated zest of a large lemon, about a heaped tablespoon

Directions:
Initial Prep:
Line the bottom and sides of a 9 inch (23 cm) square baking pan with baking paper - wet and scrunch it, then shake it dry and press into the oiled pan. Then spray the paper with vegetable oil, or butter it.
Make the oat flour unless you have it store-bought. Chop the walnuts. Melt the butter. Use a zester or microplane/grater to make the lemon zest, and squeeze the juice. Set all aside.

Oatmeal crumble:
In a large bowl put the rolled oats, oat flour, baking powder, salt, dried coconut, erythritol/brown sugar, psyllium, chopped walnuts, and mix well until combined. Add the melted and cooled butter, along with the vanilla extract and cream, and stir well until it's a crumbly mixture. Evenly press about 2/3 of the crumb mixture into the bottom of the prepared pan.

Lemon Filling:
Preheat oven to 350 degrees F (180 degrees C) and put the oven rack in the centre of the oven.
Put the condensed milk in a medium sized bowl. Whisk in the lemon zest, cornflour, and lemon juice until combined. It went thick, then weirdly foamy so I waited for that to settle. Pour the filling over the crust then cover with the remaining crumb mixture. Bake for about 45 minutes until set, covered with aluminium foil if using a mini-oven, then uncovered for the last 15 min. Remove from the oven and set aside to cool completely.

To Serve:
Let it cool. Lift the slice from the pan by the edges of the paper. Allow it to cool completely then remove the paper carefully and cut it into squares. The slice (aka bars in the USA) can be covered and stored in the fridge for about 4-5 days. Or it can be frozen. But it probably won't last as long as 5 days! Seriously yummy.

Notes:
To make it non-dairy/vegan, sub the butter with coconut oil, the cream with plant milk, and use condensed milk made from coconut milk. Alternatively, use an equivalent amount of coconut cream and mix in sugar/sweetener until sweet enough.