Preheat oven to 350 degrees and grease or line your muffin tin. If greasing, grease generously with vegan butter or coconut oil or a spray oil - then add a dusting of flour. (The flour is optional.) Set aside. TIP: See post for details, but definitely grease the entire tin, even the edges of the wells, since these muffins and the crumble will arch over a bit.
Add the tofu, oil, vanilla and lemon juice to a blender. Blend from low to high until smooth and silky - no clumps.
Pour the tofu mixture into your large mixing bowl and add all the dry ingredients, including the sugar, flour, rolled oats, salt, baking powder and optional cinnamon. Beat with a mixer - or a sturdy whisk will also work. This batter will feel heavier and thicker than a usual muffin batter, that is because the fruit gives off so much moisture.
Fold the berries into the batter - watch how it loosens up a bit from the liquid. Tip: Fold in the strawberries first - more vigorously, then gently fold in the blueberries. Blueberries tend to stain the batter a bit more. Especially if using thawed frozen berries like I did.
Add the crumble ingredients to a small bowl and use your hands to squish the crumble together. You are basically squishing the butter with the flour and sugar to form small crumbly bits.
Scoop batter into muffin tins, then top with a generous amount of crumble.
Bake muffins for 28-35 minutes at 350 degrees. Or until the edges of the tops start to brown and the muffins are nice and poofy - yet firm to touch on the top.
Cool in tin for at least ten minutes before carefully removing. They will be delicate and some of the crumble might stick to the edges of the pan.