Preheat oven to 400°F and line a baking sheet with parchment paper.

In a food processor, pulse the flour, sugar, baking powder, baking soda, and salt until combined.

Pulse in the cold butter until well dispersed, about 30 pulses.

Crack the egg into a glass measuring cup, add enough cream to make 1 cup, stir in the vanilla paste and whisk to combine.

Transfer the flour mixture to a large bowl and add the liquid ingredients, mixing just until the dough comes together (it will still be crumbly).

Turn out the dough onto a lightly floured surface and knead briefly to form a flat disk, ensuring no dry flour remains. If the dough seems too dry, add a little more cream.

Roll out the dough gently to about 3/4 inch thick and cut out 8 scones using a 3-inch biscuit cutter, reforming the dough as necessary.

Place the scones on the prepared baking sheet and refrigerate for 10 minutes.

Place the sliced rhubarb and 1 cup of sugar in a saucepan, along with 1/4 cup water.

Bring to a simmer over medium heat, stirring to dissolve the sugar. Let it gently bubble until the rhubarb softens, about 5-8 minutes.

Stir in the vanilla bean paste and remove from heat.

Brush the tops of the scones with a bit of cream and bake for about 15-17 minutes, or until they have risen and are just starting to turn golden. Avoid overbaking.

To serve, split the scones with a fork, spoon some of the rhubarb compote over one half, add whipped cream, and top with the other half of the scone.