01 - Combine warm milk and yeast in a small bowl. Let sit for 5 minutes until foamy.
02 - Whisk together flour, sugar, and salt in a large mixing bowl.
03 - Add melted butter, eggs, vanilla, and the yeast mixture to the dry ingredients. Mix until a shaggy dough forms.
04 - Knead by hand or mixer with a dough hook for 6–8 minutes until smooth and elastic.
05 - Place dough in a greased bowl, cover, and let rise in a warm place for 1 hour or until doubled in size.
06 - Add a few drops of each food coloring to each bowl of sugar and rub with fingers until evenly colored. Set aside.
07 - Turn dough onto a floured surface. Roll out to 1/2-inch thickness. Cut out 3-inch rounds with a donut cutter.
08 - Place donuts on parchment-lined trays, cover lightly, and let rise for 30 minutes.
09 - Heat oil in a large, heavy pot to 350°F.
10 - Fry donuts in batches for about 1–2 minutes per side until golden brown. Remove with a slotted spoon and drain on paper towels.
11 - Whisk together powdered sugar, milk, and vanilla until smooth.
12 - Dip warm donuts into icing, allowing excess to drip off. Immediately sprinkle with colored sugars in sections or stripes to create a traditional Mardi Gras effect. Let set for 10–15 minutes before serving.