Mix flour, BP, cocoa, salt, and sugar in a bowl.
On another bowl, mix butter, flour, sugar, cocoa, until coarse texture, then mix in mini choc chips.
Preheat oven to 400 F and grease muffin pan with melted unsalted butter.
In a food processor, mix egg, milk, oil, and essence til completely combined, then pour into the 1st bowl, mix until just combined.
Divide batter and top generously with 2nd bowl mixture.
Bake muffins for 18-20 mins