Set Instant Pot to sauté mode (see notes).
Once hot, add the oil and chopped onion to the bowl of your Instant Pot and mix well to combine. Sauté the onion, stirring often, for 3-4 minutes, or until the onion starts to soften and turn translucent. Add the finely chopped Serrano chili pepper and a dash of salt. Continue to cook for an additional 1 minute, stirring often, before stirring in the garlic and ginger. Cook, stirring continuously, for 30 seconds or so.
Reduce sauté temperature to medium-low, if needed, and stir in the garam masala, curry powder, ground cumin, paprika, and Fenugreek leaves. Cook, stirring continuously, for 1-2 minutes, taking extra care not to burn your spices as they will turn bitter. Mix in the tomato paste.
Add the canned diced tomatoes, granulated sugar, cauliflower florets, and vegetable broth. Mix well to combine.
Secure the lid and close the vent to seal. Cancel sauté mode and press the pressure cook button or “manual” mode. Set to cook for 3 minutes on “high” (see notes). Once the cooking time has completed, allow your Instant Pot to release naturally for 1 minute then manually release.
Carefully remove the lid and stir in the chickpeas, coconut milk, and ground cashews (to thicken).
Serve garnished with fresh chopped cilantro, cashews, sesame seeds, and a side of rice, if desired.