Heat the olive oil in a skillet over medium hight heat.
Season the chicken with salt and pepper and add to the skillet.
Let the chicken sear for 5 minutes, undisturbed, then flip and cook for an additional 4 minutes. Remove to a plate.
Add the butter to the pan with the mushrooms, garlic, sliced onions and thyme. Cook the vegetables for about 6 minutes, until softened.
Stir in the wine and cook for 2 minutes, until slightly reduced.
Whisk in the water and Sir Kensington's Dijon mustard.
Add the chicken and any juices to the pan and cook for 1 - 2 minutes, until reheated.
Remove from heat and add the heavy cream. Stir to coat the chicken and serve!