Blanch your diced potatoes in a large pot of boiling water for 2 minutes, then drain well and set aside.
Heat your oil and butter in a large skillet over medium-high heat.
Add potatoes to the skillet.
Stir in the onions and peppers and sauté for 3 minutes. Stir in the garlic, and season with sea salt and ground pepper to taste. (If you prefer firmer potatoes, add them in after sautéing the veggies.)
Continue to cook, stirring frequently for 8-10 minutes, or until the potatoes are tender and nicely golden brown.
Garnish with freshly sliced green onions.
Serve immediately while hot and crispy.
Store leftovers in a sealed container in the fridge for up to 4 days. Reheat in a skillet or air fryer.