Preheat the oven to 175c.
In a small bowl, mix together the psyllium husk powder and the water. Set aside to thicken.
In the bowl of a stand mixer, beat together the vegan butter and the sugar until smooth. Add the thickened psyllium husks along with the plant milk and vanilla and beat well to combine.
In a medium bowl, mix together the flour, cocoa and salt. By hand, beat the flour mixture into the butter mixture, spoon by spoon, being careful not to overwork the mix.
Using a cookie or ice cream scoop, scoop balls of dough onto a baking tray lined with baking parchment. Depending on the size of your scoop, you should get between 8 and 12 balls of dough.
Add your pecan pieces to a small bowl and, one by one, dunk the balls of dough into the pecans, making sure the pecans stick to the dough. Arrange the dunked dough back onto the baking sheet, leaving spread-room between each cookie.
Using your thumb or the back of a melon baller/coffee scoop, firmly press down the centre of each ball of dough to make a dent in the middle.
Place in the oven and bake for around 13 minutes.
Once baked, remove from the oven and use the same melon baller/coffee scoop to press down the "thumb-print' again if it has puffed up! Leave to cool fully.