Bring the water, butter, sweetener, and salt to a boil in a medium pot.

While the water boils, sift together the lupin flour, psyllium husk powder, and xanthan gum (this is important to prevent lumps in the batter).

Dump all the sifted dry ingredients into the boiling water and cook, stirring constantly with a spatula over medium heat until the dough comes together in a ball and pulls away from the sides of the pan. Some oil may separate but it will incorporate back in later.

Allow the batter to cool until you can touch the pan and then beat in eggs one at a time. Mix well until completely smooth. The batter should just fall from the spatula (it is more stiff than a traditional choux pastry).

Transfer the batter to a piping bag (or a ziplock bag and then trim the corner). Pipe 12 mounds onto a parchment or silicon lined baking sheet. Use a wet finger to press any raised tips down.

Bake in a preheated 375ºF oven for 10 minutes then reduce the temperature to 325ºF and bake for an additional 25-30 minutes, or until golden. Prop the oven door open with a spatula to allow moisture to escape, turn off oven and let stand 15 minutes to cool slowly (to prevent collapse and allow moisture escape).

Cut small slits on the sides of each puff and return the tray to the oven. Leave in propped open oven until completely cool. If the puffs are still very wet inside, bake again for another 15 minutes and cool again with the oven propped open. I like to cut them completely in half and lay the softer inside face up and bake briefly to dry the shells further

Combine all ingredients except vanilla in a small pan and bring to a boil. Reduce heat to a simmer and cook, stirring often for 15 minutes, until thickened (it will thicken more as it cools). Off heat, stir in vanilla and let cool. Refrigerate until needed. Warm through before serving.

Split the choux and fill with a scoop of ice cream. Drizzle with the fudge sauce and serve.