Add water to a large skillet to a depth of 1/4 inch and bring to a boil over high heat.
Add cauliflower and a pinch of salt, cover and let steam for 6 to 7 minutes until the cauliflower is tender but not mushy.
Use tongs to transfer steamed cauliflower to a bowl and let it cool
In a small saucepan, melt 3 tablespoons of butter with the heavy cream over medium until combined, about 5 minutes.
Remove from heat.
In a large food processor or blender, add steamed cauliflower and the cream mixture.
Process for a few minutes until super smooth and silky—almost fluffy—pausing every minute or so to check on the puree and scrape down the sides with a spatula.
Transfer to a bowl, season to taste with salt