Write a letter to your mother, telling her how much you remember her and thanking her for the nice things which she put in your tiffin box at the time of parting. 

Examination Hall 
4th Jan. 20 XX 
Respected Mother, 
Trust this letter finds you in the best of your health. I reached back here on Monday morning. Thus a week is over. All the time I remember you heartily. Whenever I see some boy accompanied by his mother, I miss you badly. I wish to be there again. 

You cannot imagine how delicious your things were. Each friend of mine who tasted those things praised your preparations.

Rest on hearing from your side. Kindly say my best regards to my father and love to my younger brother and sister. 

Your most obedient son, 
XYZ.