For the bread pudding croutons: Preheat oven to 350°. Line a rimmed baking sheet with a silicone baking mat. Cut sliced brioche into approx. 4 pieces per slice. Lay the bread on the sheet and bake for about 15 minutes, or until the bread is toasted and dry, but not browned.
Place the bread crumbs in a large bowl. Melt butter and drizzle over bread, tossing lightly to coat. Pour heavy cream over the bread, and toss to ensure all pieces are coated. Let sit for 5 minutes, tossing periodically. Strain the mixture through a sieve over medium pot. Return bread to the large bowl. Reserve cream in pot.
Whisk together eggs, 1¾ cups sugar, and vanilla. Pour egg mixture over the bread and toss to ensure all pieces are coated. Let sit for 5 minutes, tossing periodically. Strain mixture through a sieve over medium bowl for 5 minutes. Return bread to large bowl. Reserve egg mixture.
In a small saucepan over low heat, bring limoncello to a simmer. Turn off heat and add dried cranberries. cover, and let sit for 10 minutes.
Stir in lemon zest and combine with bread.
Spread bread onto silicone-lined baking sheet in a single layer and sprinkle generously with ¼ cup of sugar. Bake at 350° for 20 minutes. Flip the bread and sprinkle with remaining sugar. Bake for another 20 minutes.
Meanwhile, for the custard, heat reserved cream and 2½ tablespoons of sugar in a pot over medium-low heat, and bring to a simmer. Temper the egg mixture into the cream by slowly streaming the hot cream into the eggs while rapidly whisking the mixture. When all the cream has been whisked in, return the mixture to the pot and cook on medium-low until it comes to a boil, whisking constantly.
Once the mixture is boiling, cook for one more minute. Immediately strain mixture through a sieve over a bowl. Discard solids. Cover the custard with plastic wrap, making sure the plastic touches the entire surface of the custard. Refrigerate until cool, about 2 hours.
Meanwhile for the cranberry sauce: combine all ingredients in a saucepan, simmer until cranberries become plump. Remove from heat.
Pour into a blender and blend until smooth. Strain though a fine mesh sieve. Discard solids. Wrap sauce and let rest in refrigerator.
For the toffee: melt butter in a small sauce pan. Whisk in sugar and salt until melted. Cook to a golden brown about 4-5 minutes.
Immediately spread onto a silicone-lined baking sheet with an offset spatula to get the toffee as thin as you can. Let cool, then break into shards.
When custard is cooled, remove the plastic wrap and spoon on top of the serving platter. Top with bread pudding croutons and toffee pieces. Spoon cranberry sauce throughout and serve.