Poppy Seed Crumb Cake with Blackberries

For the cake:
240 ml 1 cup soy milk
80 g 1/4 cup soy yoghurt
1 tablespoon white wine vinegar
100 ml vegetable oil
2 tablespoons ground flax seeds
150 g 3/4 cup sugar
1/2 teaspoon ground vanilla
200 g 1 1/4 cup plus 2 tablespoons poppy seeds, ground (Grind them in a small coffee mill. Make sure the mill is suitable for grinding oily seeds.)
200 g 1 1/2 cups plus 3 tablespoons flour
2 teaspoons baking powder
1 teaspoon grated lemon peel
1/4 teaspoon salt
200 g black- and blueberries
For the crumbs:
100 g 3/4 cup plus 1 tablespoon flour
50 g 1/4 cup sugar
3 tablespoons vegetable oil

Preheat the oven to 200°C and line a round pan (20 cm diameter) with parchment paper or grease the pan.
In a bowl combine milk, yoghurt, and vinegar and let sit to curdle for 2 minutes.
Stir in remaining liquid ingredients plus flax seeds.
Stir in sugar, vanilla, and poppy seeds.
Mix with remaining ingredients.
Stir in 3-4 tablespoons of the berries and pour the batter into the prepared pan.
Place the remaining berries on top and prepare the streusel topping by combining all ingredients in a bowl.
Form large crumbs with your hands and place on top of the cake.
Bake for 45 - 50 minutes or until an inserted toothpick comes out clean.
Let the cake cool for 15 minutes. Remove pan and let cool completely before serving.