Preheat the oven to 375°F.
Add the walnuts to a blender or food processor and blend until they are a rough, flour-like texture. It's ok if there are a few small chunks, as they add texture.
In a bowl, mix together the walnuts, flour, salt, baking powder, espresso powder, and monk fruit sweetener.
Add the egg, oil, almond milk, and vanilla to the dry ingredients, and mix well. The batter should be thick, almost like cookie dough.
Spoon the batter onto a Silpat-lined baking tray. I like to add one spoonful and shape it so it is round, then add another spoonful on top of that. Divide the batter into 4 mounds.
Place a walnut on top of each muffin top or sprinkle walnut pieces onto each mound.
Bake for 18-20 minutes at 375°F. I use a gas oven. Oven temperatures vary, so make sure to take a peek at them around the 18-minute mark.
Let them cool for a couple of minutes, so they release easily from the Silpat.
Enjoy warm or at room temperature.