Preheat the oven to 425 degrees. Cut the carrots in half lengthwise and crosswise. Place in a bowl and toss with the olive oil, salt and pepper, and thyme leaves.
Heat cast iron skillet in the oven for 5 minutes. Now add carrots and roast for 20 to 25 minutes, stirring the carrots every 10 minutes.
While the carrots are in the oven, place the cumin and coriander seeds in a mortar and grind using the pestle. Add the soft butter, turmeric, chili powder, and mash with the pestle.
Remove the carrots from the oven when done. The carrots should look slightly tender & caramelized.
Add the spiced butter to the carrots and & finish with freshly chopped mint. Toss, taste, and add salt and pepper. Enjoy!