Black Bean “Jajang” Bolo Rice

Name: Black Bean “Jajang” Bolo Rice
Ingredients: 1 small onion, coarsely chopped; 2 celery stalks, coarsely chopped; 3 small carrots, peeled, chopped; 4 garlic cloves, coarsely chopped; 2 Tbsp. unsalted butter; 1 Tbsp. vegetable oil; Kosher salt; 1 14.5-oz. can crushed tomatoes; 1 cup dry red wine; 8 oz. ground beef; 8 oz. ground pork; 6 Tbsp. roasted black bean paste; 3 Tbsp. oyster sauce; ½ tsp. freshly ground black pepper; 4 cups low-sodium beef broth; 1 Tbsp. cornstarch; Steamed short-grain white rice, thinly sliced cucumber, and toasted sesame seeds (for serving)