Boil the sweet potato chunks in unsalted water until a knife slides through with no resistance, 20 to 25 minutes. Drain and let them steam dry in the colander for 5 minutes.

Blend the hot flesh until silky, then push the puree through a fine mesh sieve. Do not skip the sieve, any fiber left behind becomes a stringy streak in the set block.

Whisk the agar agar powder into ½ cup of the water and let it bloom for 10 minutes.

In a wide heavy pot, stir the remaining 1 cup water, the sugar and the glucose syrup over medium heat until the sugar dissolves. Add the sieved puree, salt, lemon juice and vanilla.

Cook over medium to medium-low heat, stirring constantly and scraping the whole bottom of the pot, for 30 to 40 minutes. The mass is ready when a spatula track stays open for two to three seconds, a spoonful holds a domed mound on a frozen plate, and a thermometer reads 221 to 225 degrees F.

Stir in the bloomed agar and bring the mass to a full rolling boil. Keep it boiling and stirring for a full minute. A simmer will not activate the agar and the paste will not set.

Pour into an 8x4-inch loaf pan lined with plastic wrap, rap the pan on the counter to level it, cool to room temperature, then refrigerate overnight.

Lift the block out by the plastic overhang and slice into ½ inch slabs with a thin knife dipped in hot water and wiped between cuts. Serve with equal slabs of fresh cheese.