Start a large pot of water on to boil while you preheat the oven to 375 F. When the water comes to a boil, add the diced potatoes. Boil for 5 minutes—no longer or they will start to fall apart. Pour them gently into a colander and allow all the water to drain off.
Place the potatoes on a baking sheet that has been lined with parchment paper or a silicone baking mat. Bake for 15 minutes and then stir with a spatula, making sure they aren’t sticking to the pan. Bake for about 20-30 more minutes, stirring again halfway through. The potatoes should become crispy but not hard and overdone.
While the potatoes are cooking, make the sauce. Sauté the onion in a non-stick pot for about 3 minutes. Add the garlic, paprika, and cayenne and cook one minute more. Add the remaining ingredients (except parsley) and simmer for about 20 minutes, until thickened. Remove the bay leaf and puree the sauce in a blender or food processor. Return it to the pan and keep warm until ready to serve.
Once the potatoes are cooked, place them in a serving bowl and pour the sauce over the top. Sprinkle with parsley and serve as a side dish or appetizer.