For the bangers: Put the cumin and fennel seeds in a small saute pan and toast over low heat, stirring occasionally, until fragrant, about 5 minutes. Transfer the seeds to a spice grinder and grind to a powder.
Put the pork chunks through a sausage grinder into a bowl. Add the ground cumin and fennel and the chiles, sprinkle with salt and pepper and mix together. Cover and refrigerate for at least 30 minutes and up to 2 hours to allow the flavors to meld.
Divide the pork mixture into sixteen 3-inch patties, each about 3 ounces. Wrap each patty in caul fat.
Heat 2 tablespoons of canola oil in a large nonstick saute pan over high heat until it begins to shimmer. Sear half of the patties on both sides until golden brown and the sausage is cooked through, about 5 minutes per side. Transfer to a baking sheet and repeat with the remaining patties.
For the kale pesto: Heat 2 tablespoons of the oil in a large saute pan over low heat. Add the garlic and cook until lightly golden brown and soft; transfer the garlic to a food processor.
Increase the heat to high, add the kale and a splash of water to the pan and cook, stirring occasionally, until the kale is soft. Transfer the kale to the food processor and add the parsley, Parmesan, green onions, the remaining 1/4 cup oil and some salt and pepper and pulse until smooth. Transfer to a bowl.
For the mash: Put the potatoes in a large saucepan, cover with cold water by 2 inches and add 2 tablespoons kosher salt. Bring to a boil and cook until tender, about 25 minutes.
For the beer-mustard gravy: While the potatoes are cooking, melt the butter in a medium saucepan over medium heat. Add the shallots and cook until soft. Add the flour and cook for 1 minute. Whisk in the beer and cook until completely reduced. Add the chicken stock, turn up the heat and cook, whisking occasionally, until thickened and the flour taste has been cooked out, about 5 minutes. Remove from the heat, whisk in the honey and mustard and season with salt and pepper. Keep warm.
To finish the mash, drain the potatoes well, return them to the pan and return the pan to the burner to dry them out for a minute. Run the potatoes through a food mill set over a large bowl. Add the warm cream and butter and mix until smooth. Fold in the mascarpone and season with salt and pepper. Add some of the kale pesto and marble in until swirled.
To finish the bangers: Top each of the patties with some of the grated Cheddar and place under the broiler until melted and bubbly.
Serve the bangers with the mash and beer-mustard gravy.