Heat the olive oil and butter in a large saucepan over medium heat. Add the shallots and sauté, stirring occasionally, until translucent, 5 to 6 minutes.

Add the dill, tomato paste, half a can of the crabmeat, the vermouth, 2 cups of the chicken stock, and a little salt and pepper. Bring to a boil, then reduce the heat slightly and simmer briskly, stirring occasionally, until reduced by half. Strain the reduction through a cheesecloth-lined sieve into a large stockpot, pressing down firmly to extract all liquid from the solids.

Add the remainder of the chicken stock as along with the sherry. Bring to a boil; then, reduce the heat and simmer for about 10 minutes. Stir in the cream.

In a separate small saucepan, make a roux by melting the butter over medium heat and whisking in the flour. Continue whisking for about 2 minutes. Then slowly stir the roux into the soup, whisking it until the soup thickens slightly.

To serve, portion the remaining crab into soup bowls and pour the hot soup over it. Garnish with dill.