French Braised Short Ribs in Red Wine Sauce

Ingredient	Quantity
Bone-in short ribs	10 (about 3 lbs)
Vegetable oil	¼ cup
Carrots (bias-cut)	3
Celery stalk (bias-cut)	1
Leeks (roughly chopped)	2
Garlic cloves (minced)	3
Tomato paste	2 tablespoons
Red wine	1 cup
Beef broth	½ cup
Fresh thyme	3 sprigs
Fresh rosemary	1 sprig
Unsalted butter (softened)	1 tablespoon
All-purpose flour	2 cups + 2 tbsp
Kosher salt	To taste
Freshly cracked black pepper	To taste
Fresh chives (optional garnish)	To garnish