Preheat oven to 400°F.
Cut the head of the garlic bulb off and drizzle with 2 teaspoons of the oil. Cover and wrap tightly in foil.
To a sheet pan, add the wrapped garlic along with jalapenos (cut in half) and onions. Drizzle the jalapenos and onions with the remaining oil.
Pop in the oven to roast. After 15 to 20 minutes, check on the jalapenos. If softened and darker in color, remove from the oven to cool. Let the onions and garlic continue roasting. After 10 more minutes, the onions and garlic should both be done. The onions will be golden and have some char marks. The garlic will be golden and completely soft.
Allow the vegetables to cool and then finely dice the roasted jalapenos and onions. Mash the garlic as well to make a paste.
To a food processor, add the feta, olive oil, lemon juice, lemon zest, salt, black pepper, and roasted garlic.
Puree until you have the consistency of a very thick spread with small chunks.
Transfer to a bowl and add the plain yoghurt, diced onion, and jalapeno. Mix together well.
Serve with pita chips to enjoy!