Melt 1/4 cup of the butter in a large skillet over medium-high heat.
Add the minced garlic and chopped onion, then sauté for about 2 minutes.
Stir in the shrimp stock and crushed bouillon cube.
Allow it to simmer while stirring occasionally.
In a separate saucepan, melt the remaining 1 1/4 sticks of butter.
Continue to cook until it turns golden brown, then set aside.
Season the catfish fillets on both sides with Cajun seasoning and add to the skillet.
Cook each fillet over high heat until the underside is deep brown, around 2 minutes.
Turn the catfish over, then add 1 teaspoon of the browned butter on top of each fillet.
Continue cooking until the other side is nicely browned as well.