While you're peeling and cutting the potatoes into 1-inch chunks, finely dice the onion and shred the cabbage into 1/4-inch strips. Heat the butter and olive oil in your Instant Pot using the sauté function on medium-high heat. Once the butter is foaming, add the diced onion and cook for 2-3 minutes until softened and fragrant. The butter-oil combination creates a richer flavor base than using just one fat, which is key to authentic colcannon.

Add the shredded cabbage to the pot and cook for 3-4 minutes, stirring occasionally, until it begins to soften and wilt. This initial cooking draws out the cabbage's moisture and creates a more cohesive filling rather than chunky pieces. Once wilted, add the prepared potatoes and water to the pot, stirring gently to combine everything evenly.

Lock the Instant Pot lid and set to cook on high pressure for 5 minutes. This timing is perfect for 1-inch potato chunks—they'll be fork-tender without becoming waterlogged. Once the timer beeps, carefully release the pressure using the quick-release method (or natural release if you prefer a slightly creamier texture).

Open the pot carefully and pour in the cream, then add the garlic powder, salt, and pepper to taste. Using a potato masher, gently mash the potatoes and cabbage together until you reach your desired consistency—I like to leave it slightly chunky for texture rather than completely smooth. Add the chopped chives just before serving so they stay bright and fresh. Taste and adjust seasonings as needed, keeping in mind that good-quality butter like Kerrygold has its own subtle richness that rounds out the dish beautifully.

Transfer the colcannon to a serving dish or individual bowls. Top each serving with a pat of butter that will melt into the warm potatoes, creating an extra layer of richness and shine.