Heat large skillet over medium-high heat. Add chopped bacon and cook until crispy. Using a slotted spoon, transfer cooked bacon to paper towel-lined plate and pour off all but 1 tablespoon bacon fat.
Return skillet to stove. Add onion and garlic; sauté 2 minutes, stirring frequently. Add diced chicken and frozen corn; sauté for an additional 3 minutes, stirring often.
Remove skillet from heat and transfer contents to pressure cooker. Add chicken broth, potatoes, salt and pepper. Close and seal pressure cooker, making sure the vent is in the sealed position. Cook on high for 8 minutes.
While the chowder cooks, make a slurry by whisking cornstarch (or flour) into milk. Set aside.
When done, remove pressure cooker from heat. Allow pressure to release on its own or carefully quick-release pressure after a few minutes. Stir in the cornstarch-milk slurry. Cover and allow chowder to thicken for 10-15 minutes before serving.
Portion soup into bowls, or homemade bread bowls (recipe below), and generously top with bacon. Garnish with green onion and cream or half-and-half, if desired. Season with additional salt and pepper, to taste.