Cook the gnocchi according to the package directions. Drain and set aside.
In a small saucepan, bring the chicken broth to a boil over medium heat. Reduce the heat to low and let it simmer until it reduces by half, about 5 minutes.
In a separate pan, heat the olive oil over medium heat. Add the chopped onions and cook for 5-7 minutes, stirring occasionally, until the onions are soft and golden brown.
Add the thawed mixed vegetables to the pan and sauté for another 2-3 minutes.
Stir in the cooked diced chicken breast and the reduced chicken broth. Add salt and pepper to taste.
Add the cooked gnocchi to the pan and gently stir to combine.
Pour the heavy cream over the chicken and gnocchi mixture and let it simmer for 2-3 minutes.
Transfer the mixture to a casserole dish and sprinkle the seasoned breadcrumbs over the top.
Bake for 10-12 minutes or until the breadcrumbs are golden brown and the casserole is bubbly.