01 - In a large mixing bowl or stand mixer, combine bread flour, yeast, granulated sugar, salt, and ground cinnamon. Mix briefly to combine dry ingredients evenly.
02 - Add warm water and melted butter to the dry mixture. Mix until a shaggy dough forms, then knead for 8–10 minutes until smooth and elastic.
03 - Place dough in a lightly oiled bowl, cover, and let rise in a warm place until doubled in volume, approximately 1 hour.
04 - While dough rises, mix brown sugar and cinnamon in a small bowl until well combined for the filling.
05 - Turn dough onto a floured surface and roll into a 10x16-inch rectangle. Spread softened butter evenly over the surface, then sprinkle with the cinnamon-sugar mixture.
06 - Starting from a long edge, tightly roll the dough into a log. Cut into 8 equal pieces. Roll each piece into a 10-inch rope and join ends to form a bagel shape, pinching firmly to seal.
07 - Place shaped bagels on a parchment-lined baking sheet, cover, and let rise for 30 minutes until slightly puffed.
08 - Preheat oven to 400°F.
09 - Bring water and honey to a boil in a large pot. Working in batches, boil each bagel for 45 seconds per side. Remove with a slotted spoon and return to the baking sheet.
10 - Bake bagels for 20–25 minutes until golden brown. Transfer to a wire rack and let cool completely.
11 - Whisk powdered sugar, milk, and vanilla extract until smooth and pourable. Adjust consistency with additional milk if needed.
12 - Drizzle glaze over cooled bagels. Immediately sprinkle with purple, green, and gold sanding sugar in sections to create the traditional Mardi Gras color pattern.