1- First of all, we should make a syrup (sherbet) for the dessert (pudding). Put your whole sugar and 3-4 Cups water (120-130ml) in a small saucepan. Then, place the saucepan over the heat. Heat must be low. And then, stir water and sugar mixture until the sugar dissolved. Bring to the boil, still stirring, and remove any white froth with the wooden spoon if that forms on the surface of saucepan. Add the lemon juice and continue to cook and stirring, for more 3-5 minutes. Set aside to cool.
2- Melt the butter in a saucepan over low heat. Then add your all purpose flour, little by little, and keep stirring (Dont forget to stir constantly because stirring process is really very important). Stirring until you have a roux with your flour and the taste of flour has been cooked out (it takes nearly 10 minutes).
3- Then, add the nuts (walnut, Hazelnut or pine nut), continue to stir for more two or three extra minutes, then carefully add the syrup (watch out for spatter). Please dont stop, change your arm but dont stop, stir constantly. If you dont want flour balls in your halva, stir constantly, until the whole your syrup is soaked. Now, it will get harder to stir but you should keep stirring, dont stop.Then cover and continue cooking over very low heat for 5-7 minutes. Spread the still - hot pudding on a plate, and cut the helva into diamonds or small squares. If you want, you can make your own shape by your hands or with two spoons give flour halva some sort of spoon - shape. Serve warm or cold.