BEST DONUT RECIPE

2 (.25 ounce) envelopes active dry yeast ¼ cup warm water (105 to 115 degrees) 1 ½ cups lukewarm milk ½ cup white sugar 1 teaspoon salt 2 eggs ⅓ cup shortening 5 cups all-purpose flour 1 quart vegetable oil for frying ⅓ cup butter