Preheat oven to 400°. Line a rimmed baking sheet with 2 sheets of foil. Spray 7 (8-ounce) ramekins with baking spray with flour.
On prepared pan, toss together carrots, garlic, melted butter, chopped sage, and ½ teaspoon salt.
Bake until carrots are fork-tender, 15 to 20 minutes.
In the work bowl of a food processor, combine warm carrot mixture and ¼ cup milk. Pulse until smooth, stopping to scrape sides of bowl.
In a small saucepan, combine carrot mixture and remaining 1 cup milk. Heat over medium heat until steaming. (Do not boil.)
In a medium saucepan, melt butter over medium heat. Add flour, and vigorously stir with a wooden spoon until combined, being careful not to let mixture brown, about 1 minute. Add hot carrot mixture, and whisk until well combined. Add pepper and remaining ½ teaspoon salt, and cook, whisking constantly, until thickened, 1 to 2 minutes. Remove from heat, and whisk in egg yolks, one at a time, until combined. Stir in Gruyère until well combined. Transfer to a large heatproof bowl, and let cool slightly, 3 to 5 minutes.
In the bowl of a stand mixer fitted with the whisk attachment, beat egg whites at medium-high speed until stiff peaks form. Using a balloon whisk, fold one-third of egg whites into carrot mixture until just a few white streaks remain. Add one-third of egg whites, whisking until just a few white streaks remain. Whisk in remaining egg whites until well combined. Spoon batter into prepared ramekins, filling ramekins three-fourths full.
Bake for 20 minutes. Garnish with sage leaves, if desired, and serve immediately.
Recipe by Louisiana Cookin' at https://louisianacookin.com/carrot-gruyere-souffles/