Start by making the toffee topping. In a medium-sized mixing bowl, whisk together the the toffee bits, flour, brown sugar, and salt until combined. Pour in the melted vegan butter and stir until the mixture comes together (it should feel sort of feel like clumpy wet sand, not too dry).

To make the muffin batter, whisk together the non-dairy milk and vinegar. Set aside for 5 minutes. Combine the melted vegan butter and sugars. Whisk in the milk mixture, yogurt, and vanilla extract until smooth.

Add the flour, baking powder and salt. Use a rubber spatula or wooden spoon to fold the dry mixture into the wet until a smooth batter forms. Make sure not to overmix!

Cover the batter with plastic wrap and refrigerate for at least 1 hr or overnight.

Preheat the oven to 400°F. Line a muffin tin with muffin liners. Fill each liner ¾ full and top with 1 heaping spoonful of toffee crumble. The toffee will melt in the oven and it may seem like a mess, but trust me it creates a deliciously sweet topping. To avoid a sticky oven mess, place your muffin tin on a baking sheet then stick in the oven. Bake for 15 minutes until a toothpick inserted comes out with a few moist crumbs.

Allow the muffins to cool for 15 minutes before enjoying.