Place chicken between 2 sheets of waxed paper. Using meat mallet, lightly pound chicken until it is 1/2 inch thick. Season generously with salt and pepper.
In a large fry pan over medium-high heat, melt butter. Add chicken breasts, and cook, turning once, until golden on both sides and opaque throughout, 8-10 minutes total. Transfer chicken to a separate plate.
Keep the pan on medium-high heat, and stir mustard seeds into the pan drippings. Cook, stirring for about 15 seconds. Add the wine and broth and bring to a simmer.
Reduce heat to medium and cook, stirring until slightly reduced, 1-2 minutes.
Stir in cream and mustard and cook for 1 minute to blend the flavors.
Return chicken breast halves and any accumulated juices to the pan, reduce heat to medium, and simmer for about 1 minute. Season with salt and pepper.
Slice the chicken and divide among dinner plates. Drizzle with sauce and serve immediately.