1. Fill a wide, shallow pot with water, set over high heat and bring to 148 degrees Fahrenheit (64 degrees Celsius). You can regulate the cooking temperature of the water using a digital thermometer or use an immersion circulator cooking bath. Place the egg yolks in the water and cook, maintaining the temperature, for 45 minutes.
2. Once the egg yolks are fully cooked, transfer them to a bowl filled with room-temperature water, to cool.
3. In a pan over high heat, heat the canola oil (enough to cover the croquettes) to 375 degrees Fahrenheit.
4. Meanwhile, whisk the two whole eggs in a small bowl.
5. In a separate bowl, combine the panko, regular bread crumbs and fresh thyme.
6. Fill a third bowl with the rice flour.
7. Remove the cooked egg yolks from the bath with a slotted spoon and let drain.
8. One at a time, place the yolks first into the bowl with the rice, completely coating the yolks until they are dry.
9. Next, place the flour-dredged yolks into the bowl with the beaten eggs and completely submerge.
10. Finally, place the egg-battered yolks in the panko-bread crumb mixture.
11. Fry the croquettes in the canola oil until golden brown, about 45 seconds to one minute.
12. Drain croquettes on paper towels.