Line a pan with parchment with parchment hanging on the edges. Preheat the oven to 350 deg F (176 C). In a bowl, mix in the wet ingredients until the sugar is fully combined.
In another bowl, whisk 1 1/2 cup flour, baking powder, baking soda and salt. (Add spices of choice if you like. Add berries, or pineapple, or candied ginger if you like. Add 2 tbsp almond flour to the dry for additional texture (optional)).
Fold into the wet until just about combined. Add more flour if needed 1 tbsp at a time to make just slightly thick batter. Pour into a parchment lined pan.
In a bowl, add the dry streusel ingredient and mix well. Add the vegan butter and oil and mix it in with your fingers until well distributed and crumbly. Spread over the cake batter.
Bake at 350 degrees F for 35 to 45 mins (depends on the pan, cake height etc). Cool for 10 mins, then remove from pan. Cool completely before slicing. Store on the counter for upto 2 days, refrigerated for upto 7 days, freeze (slices) for upto a month
To make cupcakes/muffins: Bake for 22 to 24 mins for regular size muffins.