Place the cauliflower florets in an oven-safe skillet and toss with olive oil, sea salt, and ¼ tsp. ground black pepper.
Roast in the oven for 30 minutes, until the cauliflower is tender and golden.
While the cauliflower is roasting, add chopped bacon to a large skillet over medium-high heat and cook the bacon for 4-5 minutes.
Remove the cooked bacon from the pan and set aside, reserving 1 tbsp. of the rendered bacon fat.
Add in half a diced yellow onion and 8-10 diced cremini mushrooms and cook until the onion is tender.
Next, add 3 cloves minced garlic and cook for one additional minute.
In a small mixing bowl, whisk together 2 cups greek yogurt and 1 tbsp. chickpea flour.
Turn off the heat and stir in remaining ¼ tsp. ground black pepper, dried oregano, dried thyme, ¼ cup grated parmesan, and the greek yogurt mixture.
Once the cauliflower is ready, remove from the oven and gently fold in the onion, bacon, and greek yogurt mixture until the cauliflower is coated.
Return to the oven and cook for 10 minutes to heat the mixture through.
Then, sprinkle the remaining ¼ cup of the parmesan cheese evenly over the top and return the oven for 5 more minutes, until the parmesan is melted and the gratin is golden and bubbly.