Place potatoes in a dutch oven or large saucepan. Add water to cover by about an inch. Add 1 teaspoon salt to water.
Bring water to a boil and simmer until potatoes are just starting to get tender, about 15 minutes.
Add peas and simmer 5 more minutes. Drain and set aside.
Add butter to the now empty Dutch oven or saucepan and place over medium heat.
Sprinkle flour into pan and whisk it into the butter for 1 minute.
Gradually whisk in half-and-half.
Add seasoned salt and pepper. Cook and stir until thickened, about 1 to 2 minutes.
Remove from heat and add Velveeta. Stir until melted.
Return potatoes and peas to pan and mix them into the sauce.