Preheat oven to 350F degrees. Spray two 12-count muffin pans with non-stick spray or line with cupcake liners. Set aside.
Make crumb topping. In a small bowl, combine flour, salt, brown sugar, and cinnamon. Work butter into mixture until crumbly. Set aside.
In a large bowl, toss the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and cloves together until combined. Set aside.
In a medium bowl, whisk the brown sugar and eggs together until combined. Add the sweet potatoes, oil, milk, and vanilla until combined. Pour the wet ingredients into the dry ingredients and stir until just combined. Do NOT overmix the batter.
Spoon the batter evenly into 14 cups. Sprinkle on crumb topping (about 1 tablespoon per muffin).
Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean. Allow to cool completely before frosting.
Make icing: In a small bowl, combine icing ingredients. Adjust consistency as needed. Drizzle on cool muffins.