Grease the bottom and sides of four 6-ounce dariole molds or ramekins with butter, and set them aside. In a flat-bottomed steamer or small pot with a rack set on the bottom, add enough water to reach 2 inches up the sides of the pan. Cover, and preheat over low heat.
Meanwhile, in a small bowl, whisk ½ cup of the marmalade and ¼ cup of the Cointreau. Divide the mixture among the molds, and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium-high speed until light and fluffy, about 5 minutes. Add the beaten eggs little by little, stopping and scraping down the bowl and paddle as needed. With the mixer on low, add the flour, baking powder, salt, and the remaining 1 tablespoon each marmalade and Cointreau, and mix until just combined.
Divide the batter evenly among the molds. Cover the top of each with a square of parchment or wax paper and secure with a rubber band. Transfer (paper side up) to the steamer, cover, and raise the heat to medium-low. Steam just until the puddings are set, 25–30 minutes.
Meanwhile, make the toffee sauce: In a small saucepan over medium heat, add the cream, butter, and sugar. Bring to a boil, whisking occasionally, then lower the heat to maintain a strong simmer. Cook, swirling the pan once or twice, until the sauce is slightly thickened, about 2 minutes. Set aside.
Carefully remove the puddings, and discard the paper. Working quickly, invert each onto an individual serving plate, allowing any of the remaining marmalade mixture to drip down. Serve hot, drizzled with the toffee sauce to taste.