Butternut Squash Muffins with a Frosty Top

Name: Butternut Squash Muffins with a Frosty Top
Ingredients: 14 ounces butternut squash, skin on, deseeded and roughly chopped; 2 1/4 cups light soft brown sugar; 4 large free-range or organic eggs; Sea salt; 2 1/2 cups all-purpose flour, unsifted; 2 heaping teaspoons baking powder; 1 teaspoon ground cinnamon; Handful of walnuts, chopped; 3/4 cup extra-virgin olive oil; 1 clementine, zested; 1 lemon, zested; 1/2 lemon, juiced; 1/2 cup sour cream; 2 heaping tablespoons icing sugar, sifted; 1 vanilla bean, split lengthwise and seeds scraped out; Lavender flowers or rose petals, optional