Cook vegetables following package directions. Drain and finely chop.
Meanwhile, melt butter in a large pot set over medium heat.
Whisk in flour; stir until smooth and combined. Continuing cooking and whisking until deep golden in color, about 4 or 5 minutes.
Add onion powder, garlic powder, and white pepper and whisk until combined.
Whisk stock into mixture then bring to a boil over medium-high heat, whisking slowly and constantly.
Reduce heat to medium to maintain a simmer; cook, whisking occasionally, until slightly thickened, about 10 minutes.
Stir in cooked vegetables and heavy cream. Season to taste with salt.
Portion into bowls, garnish with parsley, and serve with a lemon wedge.
