Bring milk, onions, carrots, celery, parsley, 3 shallots, garlic clove, bay leaves, salt, cloves, pepper, nutmeg and thyme just to boil in heavy 4 litre saucepan over medium heat. Remove from het, cover and let stand 30 minutes. Refrigerate until mixture is well chilled, about 2 hours. Meanwhile, melt 1 Tablespoon butter in heavy small skillet over low heat. Add remaining 4 minced shallots. Cover and cook until very soft, stirring occasionally, about 15 minutes. Puree with on/off turns in processor with pork, pork fat, eggs, flour, Port and quarter tsp garlic until smooth. Strain milk into processor, pressing down on solids to extract as much liquid as possible. Blend into puree. Transfer to large bowl. Stir in currants. Refrigerate 1 to 8 hours. (If processor has small capacity, puree in batches.) Cut sausage casings into 91 cm lengths. Tie knot at one end of each. Gather 1 piece around tip of pastry bag fitted with 1 cm plain tip. Spoon pork mixture into pastry bag, pressing down to prevent air pockets. Pipe mixture into casing, twisting casing every 15 cm to create individual sausages. Tie know at end of casing. Repeat with remaining pork and casings. Tie twists in sausage with string. Bring 8 litre water to boil in stockpot. Remove from heat and add sausages. Return pot to heat, adjusting as necessary to maintain water just below simmer (180 F). Cook until sausages are firm to touch, 20 minutes, turning occasionally. Cool in cold water to retain plumpness. Cut into individual links. (Can be prepared ahead to this point. Wrap and refrigerate up to 3 days or freeze up to 2 months.) Melt butter in heavy skillet over medium heat. Lightly brown sausages on all sides, about 8 minutes total. Serve hot. (Sausage can also be grilled.)