Chunky Chicken Chowder

Name: Chunky Chicken Chowder
Ingredients: 4 chicken thighs (bone-in and skin removed); kosher salt (to taste); pepper (to taste); 4 tablespoons butter (divided); 1 tablespoon vegetable oil; 1 large Vidalia or sweet onion (chopped); 10-12 thyme sprigs (in a bundle); 2 bay leaves; 4 cloves garlic (roughly chopped); 4 cups chicken stock; 2 russet potatoes (peeled and cut into bite-sized cubes); 8 ounces frozen white corn; 2 tablespoons all-purpose flour; 2 cups milk; 1 cup heavy cream; 1 lemon (halved, for spritzing)