For the jam: Mix the purees, sugar and lemon juice together in a saucepan over medium-high heat. Bring to a boil and add the cornstarch mixture, stirring constantly. Once fully thickened, set aside off the heat, but keep the jam warm.
For the puffs: Sift dry ingredients together. In a separate bowl, whisk together the buttermilk, melted butter and egg yolk. Adding dry to wet, whisk the ingredients together until they are just smooth. Fold in the whipped egg white.
Heat up your aebleskiver pan (see note below) over medium heat and brush each hole in the pan with a liberal amount of melted butter. Fill each hole about 90% of the way with batter. When the batter starts to bubble a little around the edges (much like pancakes), use a BBQ skewer inserted in the wet batter, to "hook" the edge of the puff and pull it up perpendicular to the pan (kind of like flipping it over halfway, the batter will pour out of your puff to refill the dip in the pan). Once the crust forms again, do another partial flip, more batter will pour out, etc. Do this once or twice more to try and create a ball. This takes practice! Once the ball has formed, keep flipping them over to ensure they don't burn while the batter fully cooks. (Alternatively, you can just flip it over all the way the first time, the final product will be more oblong than round, though.) Serve hot with the warm jam and sifted icing sugar.
Yield: approx. 1 1/2 dozen puffs

Note: if you don't have a traditional æbleskiver pan, a well-greased egg-poaching pan (the one with the dips that look like a half sphere) will do the job.