Soften currants by pouring pear brandy over them and letting them steep for at least 4 hours or up to 24 hours.
In a large skillet over medium heat, melt 2 tablespoons of the butter and 1 tablespoon of the olive oil. Add onion and sauté for 3 to 5 minutes, or until softened.
Add pear and continue cooking until softened. Add garlic and cook for another minute. Transfer mixture to a food processor and puree. Add salt, thyme, allspice, pepper, and cream cheese and process to a smooth puree. Heat remaining 1 tablespoon oil and 1 tablespoon butter in the same skillet. Add chicken livers and sauté over medium-high heat until cook through and just slightly pink, 5 to 7 minutes.
Strain pear brandy from currants, and set aside currants, and add brandy to skillet. Ignite brandy with a long match. When the flame has gone out, add liver mixture to onion-pear mixture in the food processor and process for about 30 seconds, or until mousse is smooth. Add softened currants and chopped pistachios and process until just combined, making sure currants and pistachios mousse retain their texture.
Taste for seasoning. Pour into a 4-cups crock or mold and decorate with whole pistachios and sprigs of parsley. Refrigerate for at least 4 hours or until well set. Serve with crackers or bread.