Combine 2 cups flour, Fleischmann’s® RapidRise® Instant Yeast, sugar, and salt in a large mixer bowl. In a medium microwave-safe bowl, heat milk and butter in the microwave until very warm (120°F to 130°F). Pour the milk mixture into the flour mixture, adding egg yolks. Beat for 2 minutes at low speed. Continue adding flour until soft dough forms.
Knead on a lightly floured surface until smooth and elastic (about 4 to 6 minutes). Cover and let rest for 10 minutes.
Roll out dough on a lightly-floured surface into a 12-inch circle, about ½-inch thick. Using a 3-inch cookie or biscuit cutter, cut out as many rounds as possible. Cut out the center with a 1-inch cookie cutter or poke hole through the center with finger. Place doughnuts about 2 to 3 inches apart on lightly-greased or parchment-lined baking sheet. Reroll and cut the remaining dough scraps into doughnuts until the dough is used up. Cover doughnuts and let rise for 45 minutes to 1 hour.
Heat at least 3 inches of oil in a deep fryer or deep pan to 350°F. Fry 2 to 3 doughnuts at a time, turning occasionally until well browned, about 2 to 3 minutes. Remove from oil and drain on paper towels. Cool a few minutes, then transfer to a wire rack. While the doughnuts cool, make the chocolate glaze.
FOR THE CHOCOLATE GLAZE:
Combine all of the glaze ingredients in a small, microwave-safe bowl. Microwave on high for 30 seconds and stir. Repeat until the glaze is smooth and the chocolate is completely melted.
Dip each doughnut into the glaze. Top with sprinkles if desired! Enjoy!