Preheat oven at 350 degrees. Cream butter and sugar together, then beat in eggs, bananas, and vanilla. Mix flour, baking powder, baking soda and salt in separate bowl. Add to creamed mixture atlernately with milk, beating well after each addition. Bake in greased 9x9 pan for 50-60 mins or 9x5x3 loaf pan for 60+ mins. Use toothpick to test, ready when pick is clean after poking center of bread. Cover with tin foil last 15 mins to prevent browning. *To sour milk=1/4 tbsp lemon juice or vinegar with 1/4 cup milk. Stand 5 mins For muffins, line muffin pan with liners, fill 2/3 and bake until toothpick comes out clean when inserted, about 15 minutes.