Put the bacon in a medium pot over medium heat and cook until crisp, 8 to 12 minutes. Remove to a paper towel-lined plate.
Add the scallion whites and garlic to the pot to cook in the residual bacon fat. Cook, stirring, for a minute or two, then pour in the warmed stock. Raise the heat and bring it to a boil.
Slowly whisk in the grits. Cook until the liquid is all absorbed, about 5 minutes, then stir in the cream cheese, pimentos, Cheddar, Monterey Jack, adobo, mustard, salt and pepper to taste and half of the reserved bacon. Serve garnished with the remaining bacon and reserved scallion greens.