How to cook almond walnut halwa/ Akhrot badaam ka halwa

For base
Milk 1 litre
Lemon juice 2 tbsps
Water 1 tbsps
Sugar 1 cup
Cardamom 5-6
Whole wheat flour 2-3 tbsps (make a fine paste)
Almond 100 gm
Walnut 100gm
Butter 20 gm