1 cup half and half (or, 1/2 cup heavy cream and 1/2 cup regular milk)
1 cup grated Parmesan cheese
1/8 teaspoon salt
Add quartered red potatoes to a large pot, fill with just enough water to cover potatoes. Add 1/4 teaspoon salt to the pot. Bring the pot to boil, and boil the potatoes for about 10-15 minutes, until they turn tender. Towards the end of boiling the potatoes, add frozen peas, and let the water boil for another 2-4 minutes to cook the peas. When the potatoes and the peas are both tender and cooked, drain them.
Heat olive oil and butter on medium heat in a large skillet, add minced garlic and cook for about 1 minute on medium heat, without burning.
Add half and half to the skillet with cooked garlic. Bring to boil, stirring. Once the liquid is boiling, immediately add cheese, 1/8 teaspoon salt, and keep stirring everything together (cheese and the half and half), while boiling, until the cheese melts, for about 30 seconds or 1 minute. Reduce to simmer and continue to cook, constantly stirring, to thicken the sauce - for another minute.
Immediately add cooked and drained potatoes and peas, stir them in and coat them with the sauce. Remove from heat. Taste, and add more salt if needed.