Turn on  your instant pot and choose "Saute" mode. Set time -/+  for 10 minutes.

Add vegetable oil to the bowl  of the instant pot. When it is hot, add the sliced mushrooms, season with salt and pepper to your liking. Saute for 7-8 minutes  or until golden brown. Transfer to a plate.

Then, add the whole garlic cloves and cook for 2 minutes or until lightly browned and fragrant. Remove to a plate, using a slotted spoon. Cancel "Saute" mode.

Insert the steam rack and place potatoes and broccoli on the rack. Return the cooked garlic to the bowl of instant pot. Season with salt and black pepper. Pour  1 cup of the water into the pot, close and lock the lid. Select “Pressure Cooker”  and set the cooking time for 5 min on "High". When the pot finished cooking, turn the instant pot off. Quickly release the pressure. Open the lid.

Mash potatoes, garlic and broccoli, using a masher or in a food processor. Gradually add the grated cheese and heavy cream, while mashing. Mash until smooth and then add butter. Adjust  salt and black pepper.

Add the cooked mushrooms and mix again to combine.  Garnish with fresh dill leaves or parsley. 

In a large pot heat vegetable oil. Add the  mushrooms and cook until brown. Transfer to a plate. Keep aside.

In the same pot, cook garlic until slightly browned. 

Add the potatoes to the pot, cover with water and bring to a boil. Cook for 8-10 minutes or until almost cooked. 

Finally, add  the broccoli florets and cook for 5 minutes or until tender enough to pierce with a fork easily. 

Drain the veggies in a colander. 

Proceed to mashing as described above (steps 5-6).