HEAT OVEN TO 450F/232C. Line a large sheet pan with aluminum foil (sprayed will with oil) or parchment paper. Note that parchment paper may brown on edges at this high temperature.

CUT AND BOIL POTATOES: Peel potatoes if desired and cut potatoes into 1.5 – 2 inch pieces. Place potatoes in a medium-large pot of cold water with a tablespoon of salt. Heat to boiling, then lower to medium and gently boil, uncovered, for 6-8 minutes until tender, but not too soft. Drain well in a colander or sieve.

PREPARE POTATOES FOR ROASTING: Put potatoes back the pot on medium-high heat and give them a good shake. This will dry out the potatoes and rough them up, allowing them to absorb the oil and butter better – and avoid soggy potatoes. Turn off the heat. Add butter and oil (use any combination of butter and oil as preferred to equal 5-6 tablespoons), rosemary (if using), salt, and pepper. Stir gently to coat the potatoes well. Taste and add more salt if needed.

ROAST POTATOES: Transfer potatoes to the prepared baking sheet, spreading them out in a single layer. Don't crowd the pan. Use two pans if needed. Roast for 20 minutes, turn them over, then roast for another 10-20 minutes until golden brown with crispy edges. Bake a little longer for extra crispy potatoes if you like. Serve immediately.