Thaw the frozen peas and pat them dry with paper towels. Place in a large mixing bowl.

Cook the bacon in a skillet over medium heat until crispy and golden, about 6 to 8 minutes. Transfer to a paper towel to absorb excess grease, then crumble.

Finely dice the red onion and cube the cheddar cheese. Set aside.

In a mixing bowl, combine sour cream, mayonnaise, salt, black pepper, white vinegar, and Dijon mustard. Whisk until smooth, about 1 to 2 minutes.

Add the thawed peas to the dressing and stir gently until coated.

Carefully fold in the crumbled bacon, diced onion, cheddar cheese, and most of the parsley.

Cover and refrigerate for at least 1 hour to chill.

Just before serving, stir in remaining dressing if needed and garnish with parsley.