For the lobsters: Bring a very large pot of water to a boil and have an ice bath standing by.
Separate the claws from the lobster bodies and carefully stuff each lobster tail with a spoon handle, inserting at the fan end (this will help keep the lobster tails straight as they cook). Add the lobsters and claws to the boiling water and cook for about 6 minutes. Shock in ice water until cool to the touch. Remove the spoons.
Split each lobster in half. Remove the tomalley from the lobster bodies and add to a medium heatproof bowl. Set aside. Clean out the shells of the bodies, as we will be filling them later. Set aside the lobsters on a sheet tray.
Remove the claw meat from the shell and chop. Mix the chopped claw meat with the parsley, sun-dried tomatoes, celery, capers and zest in a bowl. Set aside.
For the breadcrumbs: Melt the butter in a small saucepan and cook until browned. Place the panko, parsley and lemon zest in a blender and slowly add the brown butter until smooth. Set aside.
For the sabayon: Place the lemon juice, roe, yolks and a pinch of salt in the bowl with the tomalley and set over a small pot of simmering water. Cook, whisking constantly and occasionally removing the bowl from the pot to prevent the mixture from getting too hot and curdling, until the mixture has thickened, about 4 minutes. (The whisk should leave a trail when pulled through the mixture.) Turn off the heat but leave the bowl in place to keep warm.
For the couscous: Add the butter to a large, high-sided saute pan over medium-high heat and allow to brown. Add the Israeli couscous to the browned butter and stir to combine. Allow the couscous to toast, about 1 minute. Slowly start adding the lobster stock and cook until absorbed, continually adding lobster stock as needed (similar to risotto), until all the liquid has been absorbed, about 10 minutes.
Meanwhile, add the parsley, garlic, olive oil, walnuts, lemon zest and juice and salt to a blender and blend until smooth. Taste and adjust the seasoning as needed. Add the pesto to the couscous and stir to combine.
Preheat the broiler.
Filled the cleaned out lobster bodies with the lobster salad. Cover the lobster salad with the sabayon. Spread the breadcrumb mixture over the lobster tails. Broil the lobsters until the breadcrumbs and sabayon are browned, about 5 minutes.
Pour the couscous onto a large, shallow serving platter. Top with the broiled lobsters.