Theory:

     That night the spirit of the dog appeared to him in a dream and said, “Cut down the pine tree over my grave, and make from it a mortar for your rice pastry and a mill for your bean sauce.”
 
     So the old man chopped down the tree and cut out of the middle of the trunk a section about two feet long. With great labour, partly by fire, partly by the chisel, he scraped out a hollow place as big as a small bowl. He then made a long handled hammer of wood, such as is used for pounding rice. When New Year’s time drew near, he wished to make some rice pastry. When the rice was all boiled, granny put it into the mortar, the old man lifted his hammer to pound the mass into dough, and the blows fell heavy and fast till the pastry was all ready for baking. Suddenly the whole mass turned into a heap of gold coins. When the old woman took the hand mill, and filling it with beans began to grind, the gold dropped like rain.
Explanation:
 
After some time had passed, the dog owner returned from the grave, heartbroken at the loss of his beloved pet. He sobbed for a long time and then fell asleep. After he slept, he got a dream in which his pet dog Muko's spirit appeared. The old man's good and kind heart and his love for Muko got him connected with the spirit of his pet dog. It asked its master to cut down the pine tree under which it was buried and to make mortar for his rice pastry and a grinding mill for his bean sauce using the pine tree wood.

Though it was a dream, the old man gave importance to it and chopped the pine tree from Muko's grave and sliced a two-foot-long segment out of the middle part of the trunk. He scraped out a hollow spot the size of a small bowl with considerable effort, partly by fire, partly by the chisel. He then made a long-handled rice-pounding hammer out of wood to hit the rice in it. Also, he designed a hand mill as instructed by the dog in its master's dream. Finally, using pinewood from Muko's tomb, the couple constructed a mortar and hand mill.

It was during the New year time and the good old man wished to make rice pastry. So, they took out the mortar they created and started working with it. When the rice was done boiling, the old woman placed it in the mortar, and the old man used his hammer to smash the mass into a dough.
 
Magical mortar.png
The magical mortar
 
The blows were hard and quick, and the pastry dough was ready in no time. Then, suddenly, an incredible thing happened. The dough mass was converted into a heap of gold coins. The old couple then examined the hand mill also. When the good old woman dropped the beans inside their handmade mill and began to grind them, gold started to fall like rain out of it.
 
grinder-2934911_1920.png
The magical mill
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Mortar A strong bowl
2.
Pound To hit something very hard and making a lot of noise
3.
Mill
Refers to a machine or apparatus for grinding
4.
Pastry
Baked products such as cake
5.
Dough
A mixture of flour, water, fat etc. used for making pastry
6.
ExamineTo test
7.
Chisel
A sharp tool used for cutting or shaping wood or stone
8.
SmashTo break something
Reference:
National Council of Educational Research and Training (2007). Honeycomb. The Ashes That Made Trees Bloom (pp. 55-63). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.