To prepare the batter: Stir the beer, yeast, and sugar in a large bowl to blend then set it aside in a warm place For 15 minutes or until the yeast dissolves.
Gradually whisk in the flour to form a thick batter ensuring there are no lumps.
Cover the batter with a dry tea towel and set aside in a warm place until bubbles form, about 45 minutes.
To prepare the chips: Bring a large pot of salted water to a boil over high heat.
Cut the potatoes into 5-inch-long by 1/2-inch-thick sticks. Cook the potatoes in the boiling water for 5 minutes. Using a strainer, drain and allow the potatoes to cool completely on a baking sheet lined with paper towels.
To make the tartar sauce: add the egg yolks, mustard, and vinegar in a food processor. With the food processor running, very slowly drizzle in the oil through the feed tube until the mixture has thickened to a mayonnaise-like consistency.
Transfer the mayonnaise to a bowl, stir in the cornichons, parsley, capers and lemon juice. Season the sauce to taste with salt and pepper and refrigerate until serving.
To fry the chips: Fill a clean large wide wok or pot about halfway with oil.
Heat the oil over medium-high heat until it reaches 375°F on a deep-fry thermometer. (If you don't have a thermometer, you will know that you are at the right temperature when you throw a chip in and the oil bubbles. Adjust the heat as needed to maintain this temperature.
Season the cod with salt and pepper and dredge the cod in the flour to coat lightly.
Working in batches, dip the cod into the batter to coat and then gently lower it into the oil.
Fry until the cod is golden brown, about 6-8 minutes.
Using a slotted skimmer, remove the cod from the oil and place it onto a baking sheet lined with a rack to drain the excess oil.
Return the oil to 375 degrees F. Working in 3 batches, fry the potatoes in the oil until golden and crisp, about 4-5 minutes.
Using the slotted skimmer, transfer the chips to the baking sheet lined with a rack to drain. Season the fish and chips with salt while they are still hot.
Arrange the fish on plates with the chips and serve with the tartar sauce and lemon wedges.
For peas: Place a medium heavy based pot over medium high heat.
Add bacon and cook, stirring occasionally for about 3 minutes, until fat has rendered and bacon turns golden brown. Drain bacon and all but 1 tablespoon of fat from the pan and return pan to heat. ~Reserving cooked bacon.
Add shallots to the pot and cook about 2 minutes or until soft. Add peas to the shallots and stir to combine. Pour in stock, cover and bring to a boil. Lower to a simmer and cook 2 minutes.
Remove lid and simmer 2-3 minutes more until peas are soft enough to puree but still maintain their bright green color. Season with salt and pepper.
Using a stick blender, puree the peas until mushy but still have some texture. If the peas are too loose, place pot back over medium low heat and cook stirring constantly until some of the liquid cooks down.
Fold in mint and check for seasoning. Garnish with bacon and serve alongside fish and chips.