To make the crust: In a food processor, combine the butter and horseradish. Process until the mixture comes together. Add the bread crumbs in a stream and process until combined well. Transfer to a sheet of plastic, smooth into a thin layer and cover with another sheet of plastic. Chill.
To make the cucumbers: In a skillet set over moderate heat melt the butter, add the shallots and cook, stirring, until softened. Add the cucumbers and cook, stirring occasionally, for 3 to 4 minutes, or until just tender. Add the dill and chives.
To make the sauce: In a skillet, melt the butter with the shallots and cook, stirring occasionally, until softened. Add the vermouth and reduce by half. Add the chicken stock and reduce until flavorful. Stir in snipped fresh dill and chives.
Preheat the oven to 450 degrees F. Cut the salmon fillet into 4 portions and season with salt and pepper. In a saute pan over moderately high heat, cook the butter and oil until hot and add the salmon. Sear both sides. Divide the crust among the salmon fillets and transfer to the oven. Bake for 5 minutes.
Arrange cucumbers on a serving plate, top with the salmon and serve with the sauce.
