Preheat oven to 350ºF. Prepare an 8 1/2- by 4 1/2-inch loaf pan by greasing it or lining it with parchment paper (allowing an overhang on sides).
In a large bowl, whisk together flour, sugar, baking soda, salt and spices.
In a separate bowl, whisk together pumpkin puree, yogurt, melted butter and egg.
Using a rubber spatula, scrape the pumpkin mixture into the flour mixture and gently fold it in until just combined.
Scrape batter into prepared loaf pan and smooth out the top. Bake in centre of oven for 45-55 minutes, until top springs back when gently pressed in the middle. Cool completely on a wire rack before icing.
Whisk together ingredients for icing, adding a bit of milk if needed to achieve drizzling consistency. Spoon icing over cooled loaf.