Weigh the ingredients and prepare. Combine cake flour, strong bread flour, baking powder together and sift together. Bring the butter to room temperature.
For the filling ingredients, put all the ingredients for the filling in a pan except the almond and cake flour while weighing them. Then there would be less dishes to wash and you can save time and effort.
Coat the sliced almonds with 1 tablespoon of flour. Start to preheat the oven to 180C.
Make the cookie dough. Add sugar to the room temperature butter and mix well. Then add beaten egg a little at a time and mix well.
Add the sifted flours and mix.
Line parchment paper on the cake pan, and pour the dough in the cake pan. Cover the dough with a cellophane wrap and use your palm to even out the thickness.
Depending on how soft the butter is, the dough might become loose. In that case, you can use a spatula to even out the dough.
Take off the cellophane wrap and bake in a 180C oven for 10 minutes. It's fine if the dough becomes half baked like in the picture!
Make the filling. Put all the ingredients except the almond in a pan and heat over medium heat. When the ingredients become a little bit thick and sticky, add the almonds. Mix and then turn off the heat.
No need brown the filling, it will get a nice color when baking. The filling hardens as it cools, so pour it on the cookie bottom quickly so it coats evenly.
Bake in a 180C oven for 15 minutes. Depending on the oven, the brown color might not be enough, so add 1 minute more at a time while checking how brown it's becoming.
When it's slightly cool, take it out of the cake pan. Line kitchen parchment paper on a cutting board and turn the cake pan over on it. Cut the florentine into the size you like while it's still warm.
It will become easier to break when it's cool, so I recommend cutting it while it is still warm. Let the florentine cool completely on a grill, and then it is ready.
If you don't mind the calories, make the use 150g of butter for the cookie dough I originally started making this with 150g but it became less and less every year. Now I use 120g at the lowest.