Fill a large pot with water and preheat the immersion circulator to 145°F (63°C) for juicy, tender chicken.
Pat the chicken breasts completely dry and season evenly with salt, pepper, garlic powder, and paprika.
Place chicken in a vacuum bag with olive oil and thyme, then seal tightly, removing as much air as possible.
Submerge the sealed bag in the water bath and cook for 90 minutes; the chicken will turn opaque and firm but still tender.
Remove the chicken from the bag and pat very dry with paper towels to ensure a proper sear.
Heat a skillet over medium-high until very hot, add butter, and sear chicken 45–60 seconds per side until golden brown.
Remove from heat once a light crust forms; avoid overcooking as the inside is already perfectly done.
Rest for 5 minutes, then slice against the grain and serve immediately.
