Would it be possible to use sour cream instead of creme fraiche? I have all the other ingredients on hand.

Hi Savannah, Yes you can use sour cream instead of creme fraiche. But, you have to slightly change the proportion: 250ml of sour cream with 200ml of whole milk instead of 250ml of whole milk with 200ml of creme fraiche.
Because the sour cream contains about 20% of butterfat, so less than the creme fraiche (about 45%). The butterfat is needed to set the salted custard into the quiche. I hope you enjoy the recipe,
Best

That would be just fine....I often prefer sour cream over crème fraîche as an ingredient in dishes, because it has a bit more of a tang. Just make sure it is full fat sour cream.

I don't think prevent the quiche from setting, might just taste a little different?