Remove 2-3 of the top leaves on your brussel sprouts, then very carefully trim a tiny bit of the stem, wash and cut in half. Set aside.
Heat oil in your pan over low-medium heat, then add mustard seeds. Once the mustard seeds start to pop, add in cumin seeds and curry leaves. Cook for a few seconds or until the cumin seeds become fragrant. Mix in the garlic. Add the pureed tin tomatoes, tomato puree, turmeric powder, chili powder, cinnamon powder, coriander powder, cumin powder, clove powder and salt. Cook for 2-3 minutes.
Increase the heat to medium-high, then mix in your brussels sprouts. Cook for 4-5 minutes. Pour in the water and maple syrup. Mix, cover the pan with a lid and cook for 8-11 minutes. Stirring halfway. If you want more gravy, add in additonal water. I added an extra 3/4 cup of water once I noticed the curry getting a little dry.