Preheat oven to 375°F/190°C. Grease well 24 mini muffin cups. It's best to use a silicone pan. Don't skip that part because these muffins are sticky.
In a large bowl mix together flour, pecans, baking powder, and salt.
In a medium bowl whisk eggs and sugar for 1 minute until well combined. Stir in melted butter and vanilla extract. Add the mixture to the flour mixture and mix until combined.
Divide the mixture between the muffin cups, filling them almost all the way to the top. Bake for 11-13 minutes or until a toothpick inserted into the center of the muffin comes out clean. Allow pan to cool for several minutes, then run a knife around the edges of the muffins cups, and gently remove from pan.
Muffins will keep for 5 days in the fridge. They can also be frozen for up to 2 months. To thaw, leave them at room temperature for an hour or overnight in the fridge.