"I Love You" - I love this! This is such a great take on the much used light painting technique (that is how it was done isn't it? I'd be devastated to find out it's some sparkly font in photoshop!).
I keep coming back again and again each time to examine a little closer. How did he do it?....How did he do it??......HOW THE F**K DID HE DO IT!??
Ok let's look at this logically. Where are the footprints beneath each letter and leading from one to another? Could have been removed in Photoshop quite easily but where's the body? Must have been standing either behind or beside each letter in turn. Would be possible to remove in Photoshop but ouch! That would be such a long painstaking process, to remove the body but leave the sparks. It's the sort of task that if embarked upon would lead one down the road of insanity. Thousands of hours masking off each individual spark and trail; I can't believe it was done that way. Single exposure or multiple? I can see a trail leading from the "V" to the "E" to the "Y" but not the other letters.
The wall appears flat but wait.....look where the wall meets the snow...it's not straight! Is this a clue?! Like a detective at a crime scene I feel I've spotted something that just doesn't look right but as yet can't see its significance....hmm, I wonder.

As well as the wizardry, it's also just a great photo. I love the composition. The lone figure looks so small and vulnerable. Great exposure as well in difficult circumstances. Did you do it a hundred times till you got it right? The spacing and relative size of the lettering works great with the slightly raggedy "E" in the middle. That was probably more to do with the awkward shape of the "E" than planning but it really adds something. I might have cropped just a little (very little) off the right as it feels ever so slightly unbalanced but that's quite subjective (and then a little top and bottom to keep the dimensions. Vertically it feels perfectly balanced).
I also love the colours; the warmth from the lettering leading out to the cold blue of the snow.
All in all great shot!..I hope she appreciated the gesture.

Ah I think I've just cracked it!...... You've got a special suit that makes you invisible to the camera which you removed for he final "I" and handed to your assistant who's just out of shot....
yes that must be it....