Preheat your oven to 400F. Place a roasting pan in the oven to heat.
Rub the cornish hens with olive oil and season generously with salt and pepper.
Roast the hens for 20 minutes, then baste with the rendered fat in the roasting pan.
Roast the hens to an internal temperature of 165F in the breast, another 15-20 minutes.
Remove roasting pan from the oven. Place the hens on a cutting board.
Spoon the fat from the pan, leaving any browned bits.
Place the pan over medium heat.
Deglaze with the white wine then reduce to a syrupy glaze - about 3-5 minutes.
Add the stock and reduce by half.
While the stock reduces, mix the mustard with a couple teaspoons of additional stock or water.
Add the mustard mixture and stir to combine.
Add the cream and bring to a simmer. Reduce slightly.
Quarter the cornish hens. Add any accumulated juices to the sauce and stir to combine.
Serve 1/2 hen per person.