Take 1 cup of wheat flour in a wide bowl. Add water little by little and knead into a thick, smooth dough like chapathi dough. No need to add oil or ghee while making the dough.
Place the kneaded dough in a big bowl and pour 5 cups of water over it. Let it soak undisturbed for 2 to 4 hours.
After 2 hours, mix the dough thoroughly in the water with your hands. The dough will dissolve into the water, yielding a rich, white wheat milk.
Strain the wheat milk through a fine cloth strainer, squeezing the fiber residue to extract all liquid. Discard the residue. In a bowl, melt the required ghee and mix with the cooking oil; set aside.
In a wide, heavy-bottomed or non-stick kadai, heat 1 tbsp of ghee and roast cashews until golden brown. Add the extracted wheat milk directly into the kadai and stir continuously on medium flame for about 15 minutes until it thickens like porridge. Lower the flame and add 2 to 2 1/4 cups of sugar, mixing well.
Sugar Caramelization: In another small pan on another burner, melt 1 tbsp ghee and add 1/4 cup sugar. Stir continuously on low flame until the sugar melts and turns a rich golden brown. Be careful not to overheat it, as burnt sugar turns bitter.
Immediately switch off the flame and carefully pour the hot caramelized sugar into the simmering halwa (it will splutter slightly). Stir well on medium flame until the color turns an even light brown.
Add 1 tablespoon of the melted ghee and oil mixture and mix well. The halwa will absorb the fat and turn glossy. Continue adding 1 tablespoon of ghee+oil at regular intervals as it cooks. The color will darken to a rich, deep brown.
Cook on low to medium flame until the halwa becomes completely non-sticky, leaves the sides of the kadai and rotates freely with the ladle. In the final 5 minutes, it will stop absorbing fat and start releasing ghee. Tilt the kadai slightly and collect the excess oozed ghee in a bowl (use it for regular cooking).
Transfer the glossy halwa to a serving bowl and allow it to become warm. Serve hot or warm. Store in an airtight container at room temperature for up to a week; reheat gently before serving if desired.