Preheat oven to 350 degrees. Lightly spray silicone molds of choice or line a 9 x 13 inch cake pan with parchment paper. Allow the paper to hang over the sides for easy removal. Sift the dry ingredients into a large mixing bowl until there are no lumps in the dry ingredients
Stir in the eggs, melted butter, oil, plain yogurt and vanilla until fully combined and a batter begins to form. Stir the milk in a few tablespoons at a time until the batter is thick put easily slides off of a spoon. Pour batter evenly into the prepared molds or cake pan. Use spatula to smooth the top.
Place into preheated oven and bake at 350 degrees 15 to 20 minutes until a tester comes out clean. Remove from the oven and allow to cool in the pan or molds at least 30 minutes until firm. Remove the cakes from the molds or from the pan and transfer to a wire rack.
Allow to cool completely before slicing. Once cooled cut cake slab into desired size mini cakes (1 to 1/2 inch squares) Cut each square in half horizontally to create a top and bottom. For easy cutting place the cakes in the freezer for at least 30 minutes before cutting.
Spread a thin layer of keto jam or filling of choice over the bottom portion of the cakes. (about 1/4 to 1/2 tsp of filling) Place the top portion of the cake over the filling to create mini layer cakes and very gently press the top and bottom together to seal the layers.
Place the petit fours onto a lined baking sheet and freeze for at least 30 minutes to overnight until firm. Once firm melt the chocolate until smooth and place into a wide bowl. Remove the cakes from the freezer. Place the petit fours one at a time into the chocolate and spoon the chocolate over the top of the cakes.
Let the chocolate drizzle down the sides of the cakes until the cakes are fully coated. Use fork and gently lift the cakes out of the coating. Allow the excess chocolate to drip back into the bowl. Place the coated cakes onto the lined baking sheet and freeze another 30 minutes to overnight or until the coating is firm.
Once firm remove from the freezer and serve immediately. Store leftovers in the refrigerator up to 5 days or freeze up to 1 month.