Red gar­net yam, peeled 175 g 175% Peel and use ring cut­ter to cut out tubes mea­sur­ing 4 cm / 1½ in. in diam­e­ter and 6 cm / 2¼ in thick. Water 125 g 125% Combine all and vac­uum seal. Unsalted clar­i­fied butter 27.5 g 27.5% Cook sous vide at 90 °C / 194 °F for 1 h 20 min. Salt 4.5 g 4.5% Drain and remove from bag. Cool or serve immediately. For yam chip: Red gar­net yam as needed Slice into 1 mm / 1⁄16 in sheets on man­dolin. Punch out disks that are 3 cm / 1¼ in. in diam­e­ter and reserve. Isomalt 100 g 100% Combine all and bring to a boil to make syrup. Sugar 100 g 100% Blanch yam disks in the syrup for about 15 s. Water 100 g 100% Lay on non­stick tray and dehy­drate at 62 °C / 145 °F for 12 h. Maple syrup (Grade B) 40 g 40% For sage foam: Frying oil as needed Fry sage in 190 °C / 375 °F oil for about 10 s. Sage 40 g 40% Drain on absorbent paper towels. Water 300 g 300% Combine with fried sage leaves and vac­uum seal.
Cook sous vide at 90 °C / 194 °F for 30 min.
Strain and cool sage infusion.
Sugar 100 g 100% Add and dis­solve into sage infusion. Versawhip 3 g 3% Whip with elec­tric whisk to form stiff peaks. Xanthan gum 0.45 g 0.45% Spoon over sweet pota­toes and gar­nish with yam chips.