FOR THE CAKE:
From 1966 to 1994, Sylvia Hocking of Thomaston, Maine, ran a small home-based bakery that brought her national fame for her coffee cake, blueberry muffins, raspberry buckle, and strawberry pie. She later published a cookbook, Sylvia’s Cakes & Breads: Famous Recipes from a Small Maine Kitchen. We published a handful of her recipes in the ’90s, and this cake, moist and rich with chocolate swirls, reminds us of the beauty of old-fashioned bundts.
Preheat oven to 350°. Grease a 10-inch Bundt or tube pan. Whisk together the flour, baking powder, and salt. Set aside. In the bowl of a standing mixer or, if using a handheld mixer, in a large mixing bowl, cream the butter and sugar until light and fluffy, 3 to 4 minutes. Add vanilla and mix, then add eggs one at a time, mixing well after each. Add one-third of the dry ingredients, then add half the milk. Repeat, scraping down bowl periodically. Add remaining third of the dry ingredients and mix until combined.
Divide the batter into two bowls. Add the melted chocolate and baking soda to one of the bowls and stir until evenly combined.
To make the marble effect, drop the batters into the prepared pan by the heaping tablespoon, alternating between chocolate and vanilla batches. Try to distribute the batter evenly around the pan.
Once all the batters are in the pan, bang it several times on the counter to make the batter level. Use a thin knife to swirl through the mixture several times.
Bake until a cake tester comes out clean and the cake is fragrant, 60 to 75 minutes. Run a knife around the edges, unmold onto a wire rack and let cool completely.
FOR THE GLAZE:
While cake is cooling, make the glaze: Melt the chocolate with the butter in a small saucepan or in the microwave. Add the confectioners’ sugar, boiling water, and vanilla at the same time and whisk until smooth. If the glaze seems too thick, add a bit more water. If it’s too thin, add some more sugar.
When cake is cool, set the rack over a baking sheet or cutting board. While the glaze is still warm, pour it evenly over the cake, letting it drip down the sides and onto the sheet. Let the cake sit 5 minutes before serving.