Chop mushrooms.

Heat a small pot over medium heat. Add in olive oil. Add mushrooms and stir. Let mushrooms steam, until they shrink down, and there is no water residue in the pot. Remove from heat.

Preheat the oven to 400℉ (200℃), and place a 10'' skillet on a middle rack, to heat up.

Using a blender whisk the eggs till frothy. Add the buttermilk and keep whipping till foamy and light. Add in the flour and whisk once again until smooth, light, and completely combined.

Remove the skillet from the oven and pour in the butter, then pour the batter over the butter. Add the chives and mushrooms, and return the skillet to the oven.

Bake for 20 minutes.

Remove from oven when puffed and golden.