Blow/knock somebody’s socks off
Definition 1 of 2
Pro Tip 1/3Idiomatic Surprise
Used when something is unexpectedly impressive or surprisingly good. 
The chef’s new recipe will blow your socks off.
Pro Tip 2/3Positive Shock
Indicates a high level of astonishment, usually positive. 
You'll blow your socks off with the view from the top!
Pro Tip 3/3Informal
Common in casual conversation, not suitable for formal contexts. 
Her performance is going to blow your socks off!