Preheat oven to 350 degrees.
In a Dutch oven over medium-high heat, quickly brown birds in oil on all sides.
Place apples and onions around birds.
Pour brandy over birds and let it heat for 1 minute, then carefully ignite, using a long fireplace match.
Shake pan until flames subside.
Dust top of birds with nutmeg.
Cover Dutch oven and bake until internal temperature of thigh registers 180 degrees (about 25 to 30 minutes for 1-pound birds; 35 to 40 minutes for larger ones).
Remove hens, apples and onions to a platter; keep warm in oven.
Over medium-high heat, bring pan juices to a simmer, then stir in half-and-half.
Let mixture cook 3 minutes, stirring frequently.
Season to taste with salt and pepper.
Pour around birds, and serve at once.
Garnish with slices of green apple, if desired.