Pan-Fried Chicken with Chinese Broccoli Recipe

<>1 tablespoon vegetable oil

<>2 cloves garlic

<>1 medium white onion, chopped

<>500 grams chicken thigh fillets

<>1 250-ml pack all-purpose cream

<>2 tablespoons dijon mustard

<>300 grams chinese broccoli leaves (gai lan), or kai lan, chopped into large pieces

<> salt, to taste

<> ground black pepper, to taste